| 0/0 |
2026/05/23 09:08 |
flow |
assessment-security |
44m
Results: map[DenialOfService:true Explanation:**Bug Analysis:**
The bug is an infinite loop in `handle_tx()` within
`drivers/net/caif/caif_serial.c`, which leads to an RCU stall and soft lockup.
Here is the sequence of events that leads to the bug:
1. A privileged user opens a serial port (e.g., `/dev/ttyS3`) and attaches the
`N_CAIF` line discipline to it via `ioctl(TIOCSETD)`. This creates a `caif`
network device.
2. The user closes the serial port. During the TTY teardown process,
`tty_port_shutdown()` is called, which invokes `uart_free_xmit_buf()`.
3. `uart_free_xmit_buf()` frees the UART transmit buffer (`xmit_buf = NULL`) and
re-initializes the transmit FIFO (`INIT_KFIFO(port->xmit_fifo)`).
4. Because the FIFO is re-initialized (its mask is 0), `kfifo_avail()`
incorrectly returns `1`. Consequently, `uart_write_room()` also returns `1`.
5. There is a race window where the TTY's `xmit_buf` is freed, but the `caif`
network device is still registered and up (it is unregistered asynchronously via
a workqueue in `ser_release()`).
6. If a packet is transmitted over the `caif` network device during this window
(in the reproducer, this is triggered by `aoe` broadcasting discovery packets or
`ocfs2` heartbeat traffic), the network stack calls the device's
`ndo_start_xmit`, which maps to `caif_xmit()` and then `handle_tx()`.
7. `handle_tx()` checks `tty_write_room()`, which returns `1`. It then attempts
to write 1 byte using `tty->ops->write()` (which maps to `uart_write()`).
8. Because `xmit_buf` is `NULL`, `uart_write()` immediately returns `0`.
9. `handle_tx()` sees that `0` bytes were written, does not consume any data
from the `skb`, and loops again. It repeatedly gets `1` from `tty_write_room()`
and `0` from `uart_write()`, resulting in an infinite loop.
10. Since `ndo_start_xmit` is called with bottom halves disabled (or under a
spinlock), this infinite loop causes an RCU stall and soft lockup.
**Security Impact Assessment:**
* **Exploitable:** **False**. The bug is a pure infinite loop in the kernel
control flow. There is no memory corruption, use-after-free, or out-of-bounds
access involved. It cannot be exploited for privilege escalation or arbitrary
code execution.
* **Denial Of Service:** **True**. The infinite loop causes an RCU stall and
soft lockup, which hangs the CPU core and leads to a system crash or freeze.
* **Accessible From Unprivileged Processes:** **False**. Attaching the `N_CAIF`
line discipline requires `CAP_SYS_ADMIN` or `CAP_SYS_TTY_CONFIG` privileges.
This is explicitly checked in `ldisc_open()` in `caif_serial.c`. Unprivileged
users cannot set up the vulnerable state.
* **Accessible From User Namespaces:** **False**. The capability check in
`ldisc_open()` uses `capable()`, which checks for the capability in the initial
(global) user namespace. Therefore, even a root user inside a user namespace
cannot trigger this bug.
* **Network / Remote / Peripheral / Filesystem Trigger:** **False**. The bug is
triggered by local network transmission (TX path) during a specific race window
on a locally configured TTY. While the reproducer uses an `ocfs2` filesystem
mount, it is merely a side-effect to generate local network traffic (via `aoe`
or cluster heartbeats) and not a vulnerability in the filesystem parsing itself. Exploitable:false FilesystemTrigger:false NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
|
| 1/1 |
2026/05/23 09:08 |
action |
syz-repro-to-c-repro |
0m
Results: map[SimplifiedCRepro:// autogenerated by syzkaller (https://github.com/google/syzkaller)
#define _GNU_SOURCE
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <setjmp.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>
#include <linux/loop.h>
#ifndef __NR_memfd_create
#define __NR_memfd_create 319
#endif
static unsigned long long procid;
//% This code is derived from puff.{c,h}, found in the zlib development. The
//% original files come with the following copyright notice:
//% Copyright (C) 2002-2013 Mark Adler, all rights reserved
//% version 2.3, 21 Jan 2013
//% This software is provided 'as-is', without any express or implied
//% warranty. In no event will the author be held liable for any damages
//% arising from the use of this software.
//% Permission is granted to anyone to use this software for any purpose,
//% including commercial applications, and to alter it and redistribute it
//% freely, subject to the following restrictions:
//% 1. The origin of this software must not be misrepresented; you must not
//% claim that you wrote the original software. If you use this software
//% in a product, an acknowledgment in the product documentation would be
//% appreciated but is not required.
//% 2. Altered source versions must be plainly marked as such, and must not be
//% misrepresented as being the original software.
//% 3. This notice may not be removed or altered from any source distribution.
//% Mark Adler madler@alumni.caltech.edu
//% BEGIN CODE DERIVED FROM puff.{c,h}
#define MAXBITS 15
#define MAXLCODES 286
#define MAXDCODES 30
#define MAXCODES (MAXLCODES + MAXDCODES)
#define FIXLCODES 288
struct puff_state {
unsigned char* out;
unsigned long outlen;
unsigned long outcnt;
const unsigned char* in;
unsigned long inlen;
unsigned long incnt;
int bitbuf;
int bitcnt;
jmp_buf env;
};
static int puff_bits(struct puff_state* s, int need)
{
long val = s->bitbuf;
while (s->bitcnt < need) {
if (s->incnt == s->inlen)
longjmp(s->env, 1);
val |= (long)(s->in[s->incnt++]) << s->bitcnt;
s->bitcnt += 8;
}
s->bitbuf = (int)(val >> need);
s->bitcnt -= need;
return (int)(val & ((1L << need) - 1));
}
static int puff_stored(struct puff_state* s)
{
s->bitbuf = 0;
s->bitcnt = 0;
if (s->incnt + 4 > s->inlen)
return 2;
unsigned len = s->in[s->incnt++];
len |= s->in[s->incnt++] << 8;
if (s->in[s->incnt++] != (~len & 0xff) ||
s->in[s->incnt++] != ((~len >> 8) & 0xff))
return -2;
if (s->incnt + len > s->inlen)
return 2;
if (s->outcnt + len > s->outlen)
return 1;
for (; len--; s->outcnt++, s->incnt++) {
if (s->in[s->incnt])
s->out[s->outcnt] = s->in[s->incnt];
}
return 0;
}
struct puff_huffman {
short* count;
short* symbol;
};
static int puff_decode(struct puff_state* s, const struct puff_huffman* h)
{
int first = 0;
int index = 0;
int bitbuf = s->bitbuf;
int left = s->bitcnt;
int code = first = index = 0;
int len = 1;
short* next = h->count + 1;
while (1) {
while (left--) {
code |= bitbuf & 1;
bitbuf >>= 1;
int count = *next++;
if (code - count < first) {
s->bitbuf = bitbuf;
s->bitcnt = (s->bitcnt - len) & 7;
return h->symbol[index + (code - first)];
}
index += count;
first += count;
first <<= 1;
code <<= 1;
len++;
}
left = (MAXBITS + 1) - len;
if (left == 0)
break;
if (s->incnt == s->inlen)
longjmp(s->env, 1);
bitbuf = s->in[s->incnt++];
if (left > 8)
left = 8;
}
return -10;
}
static int puff_construct(struct puff_huffman* h, const short* length, int n)
{
int len;
for (len = 0; len <= MAXBITS; len++)
h->count[len] = 0;
int symbol;
for (symbol = 0; symbol < n; symbol++)
(h->count[length[symbol]])++;
if (h->count[0] == n)
return 0;
int left = 1;
for (len = 1; len <= MAXBITS; len++) {
left <<= 1;
left -= h->count[len];
if (left < 0)
return left;
}
short offs[MAXBITS + 1];
offs[1] = 0;
for (len = 1; len < MAXBITS; len++)
offs[len + 1] = offs[len] + h->count[len];
for (symbol = 0; symbol < n; symbol++)
if (length[symbol] != 0)
h->symbol[offs[length[symbol]]++] = symbol;
return left;
}
static int puff_codes(struct puff_state* s,
const struct puff_huffman* lencode,
const struct puff_huffman* distcode)
{
static const short lens[29] = {
3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258};
static const short lext[29] = {
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0};
static const short dists[30] = {
1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
8193, 12289, 16385, 24577};
static const short dext[30] = {
0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
12, 12, 13, 13};
int symbol;
do {
symbol = puff_decode(s, lencode);
if (symbol < 0)
return symbol;
if (symbol < 256) {
if (s->outcnt == s->outlen)
return 1;
if (symbol)
s->out[s->outcnt] = symbol;
s->outcnt++;
} else if (symbol > 256) {
symbol -= 257;
if (symbol >= 29)
return -10;
int len = lens[symbol] + puff_bits(s, lext[symbol]);
symbol = puff_decode(s, distcode);
if (symbol < 0)
return symbol;
unsigned dist = dists[symbol] + puff_bits(s, dext[symbol]);
if (dist > s->outcnt)
return -11;
if (s->outcnt + len > s->outlen)
return 1;
while (len--) {
if (dist <= s->outcnt && s->out[s->outcnt - dist])
s->out[s->outcnt] = s->out[s->outcnt - dist];
s->outcnt++;
}
}
} while (symbol != 256);
return 0;
}
static int puff_fixed(struct puff_state* s)
{
static int virgin = 1;
static short lencnt[MAXBITS + 1], lensym[FIXLCODES];
static short distcnt[MAXBITS + 1], distsym[MAXDCODES];
static struct puff_huffman lencode, distcode;
if (virgin) {
lencode.count = lencnt;
lencode.symbol = lensym;
distcode.count = distcnt;
distcode.symbol = distsym;
short lengths[FIXLCODES];
int symbol;
for (symbol = 0; symbol < 144; symbol++)
lengths[symbol] = 8;
for (; symbol < 256; symbol++)
lengths[symbol] = 9;
for (; symbol < 280; symbol++)
lengths[symbol] = 7;
for (; symbol < FIXLCODES; symbol++)
lengths[symbol] = 8;
puff_construct(&lencode, lengths, FIXLCODES);
for (symbol = 0; symbol < MAXDCODES; symbol++)
lengths[symbol] = 5;
puff_construct(&distcode, lengths, MAXDCODES);
virgin = 0;
}
return puff_codes(s, &lencode, &distcode);
}
static int puff_dynamic(struct puff_state* s)
{
static const short order[19] =
{16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
int nlen = puff_bits(s, 5) + 257;
int ndist = puff_bits(s, 5) + 1;
int ncode = puff_bits(s, 4) + 4;
if (nlen > MAXLCODES || ndist > MAXDCODES)
return -3;
short lengths[MAXCODES];
int index;
for (index = 0; index < ncode; index++)
lengths[order[index]] = puff_bits(s, 3);
for (; index < 19; index++)
lengths[order[index]] = 0;
short lencnt[MAXBITS + 1], lensym[MAXLCODES];
struct puff_huffman lencode = {lencnt, lensym};
int err = puff_construct(&lencode, lengths, 19);
if (err != 0)
return -4;
index = 0;
while (index < nlen + ndist) {
int symbol;
int len;
symbol = puff_decode(s, &lencode);
if (symbol < 0)
return symbol;
if (symbol < 16)
lengths[index++] = symbol;
else {
len = 0;
if (symbol == 16) {
if (index == 0)
return -5;
len = lengths[index - 1];
symbol = 3 + puff_bits(s, 2);
} else if (symbol == 17)
symbol = 3 + puff_bits(s, 3);
else
symbol = 11 + puff_bits(s, 7);
if (index + symbol > nlen + ndist)
return -6;
while (symbol--)
lengths[index++] = len;
}
}
if (lengths[256] == 0)
return -9;
err = puff_construct(&lencode, lengths, nlen);
if (err && (err < 0 || nlen != lencode.count[0] + lencode.count[1]))
return -7;
short distcnt[MAXBITS + 1], distsym[MAXDCODES];
struct puff_huffman distcode = {distcnt, distsym};
err = puff_construct(&distcode, lengths + nlen, ndist);
if (err && (err < 0 || ndist != distcode.count[0] + distcode.count[1]))
return -8;
return puff_codes(s, &lencode, &distcode);
}
static int puff(
unsigned char* dest,
unsigned long* destlen,
const unsigned char* source,
unsigned long sourcelen)
{
struct puff_state s = {
.out = dest,
.outlen = *destlen,
.outcnt = 0,
.in = source,
.inlen = sourcelen,
.incnt = 0,
.bitbuf = 0,
.bitcnt = 0,
};
int err;
if (setjmp(s.env) != 0)
err = 2;
else {
int last;
do {
last = puff_bits(&s, 1);
int type = puff_bits(&s, 2);
err = type == 0 ? puff_stored(&s) : (type == 1 ? puff_fixed(&s) : (type == 2 ? puff_dynamic(&s) : -1));
if (err != 0)
break;
} while (!last);
}
*destlen = s.outcnt;
return err;
}
//% END CODE DERIVED FROM puff.{c,h}
#define ZLIB_HEADER_WIDTH 2
static int puff_zlib_to_file(const unsigned char* source, unsigned long sourcelen, int dest_fd)
{
if (sourcelen < ZLIB_HEADER_WIDTH)
return 0;
source += ZLIB_HEADER_WIDTH;
sourcelen -= ZLIB_HEADER_WIDTH;
const unsigned long max_destlen = 132 << 20;
void* ret = mmap(0, max_destlen, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANON, -1, 0);
if (ret == MAP_FAILED)
return -1;
unsigned char* dest = (unsigned char*)ret;
unsigned long destlen = max_destlen;
int err = puff(dest, &destlen, source, sourcelen);
if (err) {
munmap(dest, max_destlen);
errno = -err;
return -1;
}
if (write(dest_fd, dest, destlen) != (ssize_t)destlen) {
munmap(dest, max_destlen);
return -1;
}
return munmap(dest, max_destlen);
}
static int setup_loop_device(unsigned char* data, unsigned long size, const char* loopname, int* loopfd_p)
{
int err = 0, loopfd = -1;
int memfd = syscall(__NR_memfd_create, "syzkaller", 0);
if (memfd == -1) {
err = errno;
goto error;
}
if (puff_zlib_to_file(data, size, memfd)) {
err = errno;
goto error_close_memfd;
}
loopfd = open(loopname, O_RDWR);
if (loopfd == -1) {
err = errno;
goto error_close_memfd;
}
if (ioctl(loopfd, LOOP_SET_FD, memfd)) {
if (errno != EBUSY) {
err = errno;
goto error_close_loop;
}
ioctl(loopfd, LOOP_CLR_FD, 0);
usleep(1000);
if (ioctl(loopfd, LOOP_SET_FD, memfd)) {
err = errno;
goto error_close_loop;
}
}
close(memfd);
*loopfd_p = loopfd;
return 0;
error_close_loop:
close(loopfd);
error_close_memfd:
close(memfd);
error:
errno = err;
return -1;
}
static void reset_loop_device(const char* loopname)
{
int loopfd = open(loopname, O_RDWR);
if (loopfd == -1) {
return;
}
if (ioctl(loopfd, LOOP_CLR_FD, 0)) {
}
close(loopfd);
}
static long syz_mount_image(
volatile long fsarg,
volatile long dir,
volatile long flags,
volatile long optsarg,
volatile long change_dir,
volatile unsigned long size,
volatile long image)
{
unsigned char* data = (unsigned char*)image;
int res = -1, err = 0, need_loop_device = !!size;
char* mount_opts = (char*)optsarg;
char* target = (char*)dir;
char* fs = (char*)fsarg;
char* source = NULL;
char loopname[64];
if (need_loop_device) {
int loopfd;
memset(loopname, 0, sizeof(loopname));
snprintf(loopname, sizeof(loopname), "/dev/loop%llu", procid);
if (setup_loop_device(data, size, loopname, &loopfd) == -1)
return -1;
close(loopfd);
source = loopname;
}
mkdir(target, 0777);
char opts[256];
memset(opts, 0, sizeof(opts));
if (strlen(mount_opts) > (sizeof(opts) - 32)) {
}
strncpy(opts, mount_opts, sizeof(opts) - 32);
if (strcmp(fs, "iso9660") == 0) {
flags |= MS_RDONLY;
} else if (strncmp(fs, "ext", 3) == 0) {
bool has_remount_ro = false;
char* remount_ro_start = strstr(opts, "errors=remount-ro");
if (remount_ro_start != NULL) {
char after = *(remount_ro_start + strlen("errors=remount-ro"));
char before = remount_ro_start == opts ? '\0' : *(remount_ro_start - 1);
has_remount_ro = ((before == '\0' || before == ',') && (after == '\0' || after == ','));
}
if (strstr(opts, "errors=panic") || !has_remount_ro)
strcat(opts, ",errors=continue");
} else if (strcmp(fs, "xfs") == 0) {
strcat(opts, ",nouuid");
} else if (strncmp(fs, "gfs2", 4) == 0 && (strstr(opts, "errors=panic") || strstr(opts, "debug"))) {
strcat(opts, ",errors=withdraw");
}
res = mount(source, target, fs, flags, opts);
if (res == -1) {
err = errno;
goto error_clear_loop;
}
res = open(target, O_RDONLY | O_DIRECTORY);
if (res == -1) {
err = errno;
goto error_clear_loop;
}
if (change_dir) {
res = chdir(target);
if (res == -1) {
err = errno;
}
}
error_clear_loop:
if (need_loop_device)
reset_loop_device(loopname);
errno = err;
return res;
}
uint64_t r[1] = {0xffffffffffffffff};
int main(void)
{
syscall(__NR_mmap, /*addr=*/0x1ffffffff000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/(intptr_t)-1, /*offset=*/0ul);
syscall(__NR_mmap, /*addr=*/0x200000000000ul, /*len=*/0x1000000ul, /*prot=PROT_WRITE|PROT_READ|PROT_EXEC*/7ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/(intptr_t)-1, /*offset=*/0ul);
syscall(__NR_mmap, /*addr=*/0x200001000000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/(intptr_t)-1, /*offset=*/0ul);
const char* reason;
(void)reason;
intptr_t res = 0;
if (write(1, "executing program\n", sizeof("executing program\n") - 1)) {}
// openat$ttyS3 arguments: [
// fd: const = 0xffffffffffffff9c (8 bytes)
// file: ptr[in, buffer] {
// buffer: {2f 64 65 76 2f 74 74 79 53 33 00} (length 0xb)
// }
// flags: open_flags = 0x0 (4 bytes)
// mode: const = 0x0 (2 bytes)
// ]
// returns fd_tty
memcpy((void*)0x200000000080, "/dev/ttyS3\000", 11);
res = syscall(__NR_openat, /*fd=*/0xffffffffffffff9cul, /*file=*/0x200000000080ul, /*flags=*/0, /*mode=*/0);
if (res != -1)
r[0] = res;
// ioctl$TIOCSETD arguments: [
// fd: fd_tty (resource)
// cmd: const = 0x5423 (4 bytes)
// arg: ptr[in, int32] {
// int32 = 0x14 (4 bytes)
// }
// ]
*(uint32_t*)0x200000000040 = 0x14;
syscall(__NR_ioctl, /*fd=*/r[0], /*cmd=*/0x5423, /*arg=*/0x200000000040ul);
// syz_mount_image$ocfs2 arguments: [
// fs: ptr[in, buffer] {
// buffer: {6f 63 66 73 32 00} (length 0x6)
// }
// dir: ptr[in, buffer] {
// buffer: {2e 2f 66 69 6c 65 31 00} (length 0x8)
// }
// flags: mount_flags = 0x8c0 (8 bytes)
// opts: ptr[inout, array[ANYUNION]] {
// array[ANYUNION] {
// union ANYUNION {
// ANYBLOB: buffer: {61 63 6c 2c 68 65 61 72 74 62 65 61 74 3d 6e 6f 6e 65 2c 65 72 72 6f 72 73 3d 72 65 6d 6f 75 6e 74 2d 72 6f 2c 63 6f 68 65 72 65 6e 63 79 3d 66 75 6c 6c 2c 63 6f 68 65 72 65 6e 63 79 3d 66 75 6c 6c 2c 6c 6f 63 61 6c 66 6c 6f 63 6b 73 2c 69 6e 74 72 2c 6e 6f 61 63 6c 2c 00 19 67 b9 b8 a6 cd d6 36 d7 54 28 f2 c5 e8 05 4d 01 85 8e ef 55 27 55 57 6e 74 95 26 b3 68 60 cf 25 11 04 0d 1c e5 a7 43 ff d8 3d 29 d1 ba 3a 54 a5 9d 8c 7a a2 49 f0 8d 3c 8c 6d 04 ac 10 5d 67 93 4d b6 19 0d 59 f2 32 3b 55 a5 a4} (length 0xa7)
// }
// }
// }
// chdir: int8 = 0x1 (1 bytes)
// size: len = 0x442a (8 bytes)
// img: ptr[in, buffer] {
// buffer: (compressed buffer with length 0x442a)
// }
// ]
// returns fd_dir
memcpy((void*)0x200000004440, "ocfs2\000", 6);
memcpy((void*)0x200000000040, "./file1\000", 8);
memcpy((void*)0x200000000100, "... [truncated large byte array] ...", 167);
memcpy((void*)0x200000008940, "... [truncated large byte array] ...", 17450);
syz_mount_image(/*fs=*/0x200000004440, /*dir=*/0x200000000040, /*flags=MS_NODIRATIME|MS_MANDLOCK|MS_DIRSYNC*/0x8c0, /*opts=*/0x200000000100, /*chdir=*/1, /*size=*/0x442a, /*img=*/0x200000008940);
return 0;
}
]
|
| 2/1 |
2026/05/23 09:08 |
action |
kernel-checkouter |
1m
Results: map[KernelSrc:/app/workdir/cache/src/6ce1ef2d0fcd657a6560736cd360412639425beb]
|
| 3/1 |
2026/05/23 09:09 |
action |
kernel-builder |
19m
Results: map[KernelObj:/app/workdir/cache/build/fce2812b2d7268ccd04b541b4060cbc4bcc969c1]
|
| 4/1 |
2026/05/23 09:29 |
action |
codesearch-prepare |
14m
Results: map[Index:codesearch-index]
|
| 5/1 |
2026/05/23 09:43 |
agent |
expert |
9m
Model:
Results: map[DenialOfService:true Exploitable:false FilesystemTrigger:false NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
Instruction:
You are an experienced Linux kernel security engineer. Your task is to analyze given kernel bug report
and determine its security impact based on the following dimensions.
Use the provided tools to examine the source code, check for capability checks (e.g., capable(), ns_capable()),
and understand the nature of the bug. Analyze the given kernel build and configuration.
You can check the kernel config by grepping ".config" file; you can check kernel cmdline by greeping
".config" file for "CONFIG_CMDLINE=". Assume sysctl parameters have default values.
But analyze for the corresponding production build w/o debugging tools enabled (like KASAN, KMSAN, UBSAN).
Try different strategies when analyzing the bug:
- think of ways in which the vulnerable code is unreachable
- or the other way around: try to come up with different ideas of how an unprivileged user can reach the bug
If still unsure err on the side of the bug being non-exploitable/not-accessible.
In the final reply, provide a reasoning for your assessment.
Analysis dimensions:
* Exploitable:
Determine if the bug can result in memory corruption or elevated privileges.
Memory safety issues are almost always exploitable (KASAN or UBSAN reports for use-after-free, out-of-bounds;
refcounting issues, corrupted lists, etc). When kernel is crashing on a completly wild pointer access
(e.g. user-space address, or non-canonical address, but not on NULL or address corresponding to KASAN shadow
for NULL address), including both data accesses and control tranfers, that's also usually implies possibility
of exploitation. Such reports usually say "unable to handle kernel paging request".
Uses of uninitialized values detected by KMSAN may be exploitable b/c attacker frequently can affect uninit
values with spraying techniques. However, for these exploitabability depends on how exactly the uninit value
is used in the code, and what it affects.
Think of what happens after the bug is triggered. Some bugs cause kernel panic and halt execution,
they are harder to exploit. For example, BUG reports halts the kernel. However, WARNING reports don't halt
execution in production builds. Debug bug detection tools (like KASAN, KMSAN, KCSAN, UBSAN) are also not enabled
in production builds, so attacker can freely exploit these bugs w/o being detected by these tools.
If you see an integer overflow, think how the overflowed value used later (if it's used as allocation size,
or an array index). If you see an out-of-bounds read, think if it's followed by an out-of-bounds write as well.
Some KCSAN data-races may be exploitable by skilled attackers as well. Think what data structures got corrupted
as the result of data races and how. However, note that kernel has lots of "benign" data races that don't lead
to any runtime misbehavior at all.
* Denial Of Service:
Determine if the bug can result in denial-of-service. Most bugs can, since they cause system crash,
hangs, deadlocks, or resource leaks. This is mostly applicable to WARNING bugs that won't cause system crash
in production. For these think what will be consequences of the violation of the kernel assumptions flagged
by the WARNING. In some cases the unexpected condition is also properly handled by the normal control flow
(e.g. with "if (WARN_ON(...))"), these won't cause denial-of-service. If the condition is not handled,
then it may or may not cause denial-of-service.
* Accessible From Unprivileged Processes:
Determine if the bug can be reached from a typical (non-root) user process that does NOT have any special capabilities
(like CAP_SYS_ADMIN, CAP_NET_ADMIN, CAP_NET_RAW, CAP_PERFMON) or access to device nodes restricted to root.
Assume that unprivileged_bpf_disabled=1, that is eBPF loading is not accessible. However, cBPF (classical BPF)
is still accessible to non-root processes.
Assume that user namespaces are not accessible, that is, the process cannot get the mentioned capabilities even
within a new user namespace (checked by ns_capable() function in the kernel sources).
* Accessible From User Namespaces:
Determine if the bug can be reached within a user-namespace where the process has all capabilities
(including CAP_SYS_ADMIN, CAP_NET_ADMIN, CAP_NET_RAW, CAP_PERFMON). Such capabilities are checked with ns_capable()
function in the kernel sources.
* VM Guest Trigger:
Determine if the bug can be triggered from the context of a typical KVM guest (e.g., set up by a QEMU VMM).
Consider accesses to standard Linux host paravirtualized features (virtio-blk, virtio-net, etc.),
and handling of VM exits in the KVM code.
* VM Host Trigger in The Confidetial Computing Context:
Determine if the bug can be triggered in a confidential computing guest kernel from the context of a KVM host.
Consider access to standard Linux guest paravirtualized features (virtio-blk, virtio-net, etc.).
* Ethernet Network Trigger:
Determine if the bug can be triggered by processing ingress network Ethernet traffic, either directly (network stack)
or via drivers exposed to network data.
* Other Remote Trigger:
Determine if the bug can be triggered by processing remote traffic other than Ethernet (Wifi, Bluetooth, NFC, etc).
* Peripheral Trigger:
Determine if the bug can be triggered via an untrusted peripheral device that can be physically plugged
into a system, such as a USB device or a niche hardware driver handling external hardware inputs.
This is particularly important for mobile and desktop environments where users can plug in unknown devices.
* Malicious Filesystem Trigger:
Determine if the bug can be triggered by the kernel mounting and parsing a malicious filesystem image.
This is highly critical for Desktop and Mobile environments where external media or downloaded images
might be auto-mounted.
Don't make assumptions about the kernel source code (it may be different from what you assume it is).
Extensively use the provided code access tools (codesearch-*, git-*, grepper, etc)
to examine the actual source code, and confirm any assumptions.
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt:
The kernel bug report is:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-0): P5973/1:b..l
rcu: (detected by 0, t=10502 jiffies, g=33977, q=94 ncpus=1)
task:syz.5.221 state:R running task stack:25112 pid:5973 tgid:5973 ppid:5485 task_flags:0x400040 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5260 [inline]
__schedule+0x14ea/0x5050 kernel/sched/core.c:6867
preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7194
irqentry_exit+0x597/0x620 kernel/entry/common.c:216
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:__rcu_read_lock+0x31/0x60 kernel/rcu/tree_plugin.h:416
Code: 8b 1d bb 01 49 11 48 81 c3 84 04 00 00 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 0f b6 04 08 84 c0 75 18 ff 03 8b 03 <3d> 00 00 00 40 7d 07 5b c3 cc cc cc cc cc 90 0f 0b 90 eb f3 89 d9
RSP: 0018:ffffc90003b170c8 EFLAGS: 00000202
RAX: 0000000000000001 RBX: ffff8880526f8484 RCX: dffffc0000000000
RDX: dffffc0000000000 RSI: ffffffff8200ea42 RDI: ffffc90003b171a8
RBP: dffffc0000000000 R08: ffffc90003b17270 R09: 0000000000000008
R10: ffffc90003b171f8 R11: ffffffff81afb170 R12: 1ffff92000762e35
R13: ffffc90003b171e0 R14: ffffc90003b171a8 R15: ffffc90003b17b20
rcu_read_lock include/linux/rcupdate.h:865 [inline]
class_rcu_constructor include/linux/rcupdate.h:1195 [inline]
unwind_next_frame+0x9e/0x23c0 arch/x86/kernel/unwind_orc.c:495
arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122
save_stack+0x122/0x230 mm/page_owner.c:165
__set_page_owner+0x8d/0x4c0 mm/page_owner.c:341
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x228/0x280 mm/page_alloc.c:1884
prep_new_page mm/page_alloc.c:1892 [inline]
get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3945
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5240
alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486
folio_alloc_mpol_noprof+0x39/0x70 mm/mempolicy.c:2505
shmem_alloc_folio mm/shmem.c:1913 [inline]
shmem_alloc_and_add_folio+0x445/0xf80 mm/shmem.c:1955
shmem_get_folio_gfp+0x5a9/0x1670 mm/shmem.c:2579
shmem_get_folio mm/shmem.c:2685 [inline]
shmem_write_begin+0x16c/0x330 mm/shmem.c:3338
generic_perform_write+0x2e2/0x8f0 mm/filemap.c:4314
shmem_file_write_iter+0xf8/0x120 mm/shmem.c:3513
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x61d/0xb90 fs/read_write.c:686
ksys_write+0x150/0x270 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1ef735b78e
RSP: 002b:00007ffc44ca3b98 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000055558e4b7500 RCX: 00007f1ef735b78e
RDX: 0000000001000000 RSI: 00007f1eee400000 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004
R13: 00007ffc44ca3cd0 R14: 00007ffc44ca3c90 R15: 00007f1eee400000
</TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10497 jiffies! g33977 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: Possible timer handling issue on cpu=0 timer-softirq=24428
rcu: rcu_preempt kthread starved for 10498 jiffies! g33977 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=0
rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt state:I stack:28784 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5260 [inline]
__schedule+0x14ea/0x5050 kernel/sched/core.c:6867
__schedule_loop kernel/sched/core.c:6949 [inline]
schedule+0x164/0x360 kernel/sched/core.c:6964
schedule_timeout+0x158/0x2c0 kernel/time/sleep_timeout.c:99
rcu_gp_fqs_loop+0x312/0x1560 kernel/rcu/tree.c:2083
rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:2285
kthread+0x726/0x8b0 kernel/kthread.c:463
ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 1314 Comm: aoe_tx0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x47/0x80 kernel/locking/spinlock.c:194
Code: f7 e8 dd 47 05 f6 f7 c3 00 02 00 00 74 05 e8 80 b5 30 f6 9c 58 a9 00 02 00 00 75 27 f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 64 13 f7 f5 65 8b 05 cd b5 57 07 85 c0 74 18 5b 41 5e c3 cc cc
RSP: 0018:ffffc9000858f788 EFLAGS: 00000206
RAX: 0000000000000006 RBX: 0000000000000286 RCX: 0000000000000202
RDX: 0000000000000002 RSI: ffffffff8dccfc9a RDI: 0000000000000001
RBP: dffffc0000000000 R08: ffffffff8fef3f77 R09: 1ffffffff1fde7ee
R10: dffffc0000000000 R11: fffffbfff1fde7ef R12: 0000000000000000
R13: 0000000000000000 R14: ffffffff9a3421a0 R15: ffffffff8edf0cc0
FS: 0000000000000000(0000) GS:ffff88808ccea000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6c1dbf8000 CR3: 000000005495c000 CR4: 0000000000352ef0
Call Trace:
<TASK>
spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
uart_port_unlock_irqrestore include/linux/serial_core.h:788 [inline]
uart_port_unlock_deref drivers/tty/serial/serial_core.c:91 [inline]
uart_write_room+0x3b0/0x840 drivers/tty/serial/serial_core.c:647
handle_tx+0x163/0x610 drivers/net/caif/caif_serial.c:212
__netdev_start_xmit include/linux/netdevice.h:5273 [inline]
netdev_start_xmit include/linux/netdevice.h:5282 [inline]
xmit_one net/core/dev.c:3866 [inline]
dev_hard_start_xmit+0x2cd/0x7f0 net/core/dev.c:3882
__dev_queue_xmit+0x168f/0x3850 net/core/dev.c:4832
dev_queue_xmit include/linux/netdevice.h:3381 [inline]
tx+0x6b/0x190 drivers/block/aoe/aoenet.c:62
kthread+0x1e0/0x3f0 drivers/block/aoe/aoecmd.c:1241
kthread+0x726/0x8b0 kernel/kthread.c:463
ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>
It is reproducible with the followint program.
Keep in mind that it may lack the precise threading, sandboxing, and some arguments of a working reproducer.
But it should give an idea of the involved syscalls.
// autogenerated by syzkaller (https://github.com/google/syzkaller)
#define _GNU_SOURCE
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <setjmp.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>
#include <linux/loop.h>
#ifndef __NR_memfd_create
#define __NR_memfd_create 319
#endif
static unsigned long long procid;
//% This code is derived from puff.{c,h}, found in the zlib development. The
//% original files come with the following copyright notice:
//% Copyright (C) 2002-2013 Mark Adler, all rights reserved
//% version 2.3, 21 Jan 2013
//% This software is provided 'as-is', without any express or implied
//% warranty. In no event will the author be held liable for any damages
//% arising from the use of this software.
//% Permission is granted to anyone to use this software for any purpose,
//% including commercial applications, and to alter it and redistribute it
//% freely, subject to the following restrictions:
//% 1. The origin of this software must not be misrepresented; you must not
//% claim that you wrote the original software. If you use this software
//% in a product, an acknowledgment in the product documentation would be
//% appreciated but is not required.
//% 2. Altered source versions must be plainly marked as such, and must not be
//% misrepresented as being the original software.
//% 3. This notice may not be removed or altered from any source distribution.
//% Mark Adler madler@alumni.caltech.edu
//% BEGIN CODE DERIVED FROM puff.{c,h}
#define MAXBITS 15
#define MAXLCODES 286
#define MAXDCODES 30
#define MAXCODES (MAXLCODES + MAXDCODES)
#define FIXLCODES 288
struct puff_state {
unsigned char* out;
unsigned long outlen;
unsigned long outcnt;
const unsigned char* in;
unsigned long inlen;
unsigned long incnt;
int bitbuf;
int bitcnt;
jmp_buf env;
};
static int puff_bits(struct puff_state* s, int need)
{
long val = s->bitbuf;
while (s->bitcnt < need) {
if (s->incnt == s->inlen)
longjmp(s->env, 1);
val |= (long)(s->in[s->incnt++]) << s->bitcnt;
s->bitcnt += 8;
}
s->bitbuf = (int)(val >> need);
s->bitcnt -= need;
return (int)(val & ((1L << need) - 1));
}
static int puff_stored(struct puff_state* s)
{
s->bitbuf = 0;
s->bitcnt = 0;
if (s->incnt + 4 > s->inlen)
return 2;
unsigned len = s->in[s->incnt++];
len |= s->in[s->incnt++] << 8;
if (s->in[s->incnt++] != (~len & 0xff) ||
s->in[s->incnt++] != ((~len >> 8) & 0xff))
return -2;
if (s->incnt + len > s->inlen)
return 2;
if (s->outcnt + len > s->outlen)
return 1;
for (; len--; s->outcnt++, s->incnt++) {
if (s->in[s->incnt])
s->out[s->outcnt] = s->in[s->incnt];
}
return 0;
}
struct puff_huffman {
short* count;
short* symbol;
};
static int puff_decode(struct puff_state* s, const struct puff_huffman* h)
{
int first = 0;
int index = 0;
int bitbuf = s->bitbuf;
int left = s->bitcnt;
int code = first = index = 0;
int len = 1;
short* next = h->count + 1;
while (1) {
while (left--) {
code |= bitbuf & 1;
bitbuf >>= 1;
int count = *next++;
if (code - count < first) {
s->bitbuf = bitbuf;
s->bitcnt = (s->bitcnt - len) & 7;
return h->symbol[index + (code - first)];
}
index += count;
first += count;
first <<= 1;
code <<= 1;
len++;
}
left = (MAXBITS + 1) - len;
if (left == 0)
break;
if (s->incnt == s->inlen)
longjmp(s->env, 1);
bitbuf = s->in[s->incnt++];
if (left > 8)
left = 8;
}
return -10;
}
static int puff_construct(struct puff_huffman* h, const short* length, int n)
{
int len;
for (len = 0; len <= MAXBITS; len++)
h->count[len] = 0;
int symbol;
for (symbol = 0; symbol < n; symbol++)
(h->count[length[symbol]])++;
if (h->count[0] == n)
return 0;
int left = 1;
for (len = 1; len <= MAXBITS; len++) {
left <<= 1;
left -= h->count[len];
if (left < 0)
return left;
}
short offs[MAXBITS + 1];
offs[1] = 0;
for (len = 1; len < MAXBITS; len++)
offs[len + 1] = offs[len] + h->count[len];
for (symbol = 0; symbol < n; symbol++)
if (length[symbol] != 0)
h->symbol[offs[length[symbol]]++] = symbol;
return left;
}
static int puff_codes(struct puff_state* s,
const struct puff_huffman* lencode,
const struct puff_huffman* distcode)
{
static const short lens[29] = {
3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258};
static const short lext[29] = {
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0};
static const short dists[30] = {
1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
8193, 12289, 16385, 24577};
static const short dext[30] = {
0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
12, 12, 13, 13};
int symbol;
do {
symbol = puff_decode(s, lencode);
if (symbol < 0)
return symbol;
if (symbol < 256) {
if (s->outcnt == s->outlen)
return 1;
if (symbol)
s->out[s->outcnt] = symbol;
s->outcnt++;
} else if (symbol > 256) {
symbol -= 257;
if (symbol >= 29)
return -10;
int len = lens[symbol] + puff_bits(s, lext[symbol]);
symbol = puff_decode(s, distcode);
if (symbol < 0)
return symbol;
unsigned dist = dists[symbol] + puff_bits(s, dext[symbol]);
if (dist > s->outcnt)
return -11;
if (s->outcnt + len > s->outlen)
return 1;
while (len--) {
if (dist <= s->outcnt && s->out[s->outcnt - dist])
s->out[s->outcnt] = s->out[s->outcnt - dist];
s->outcnt++;
}
}
} while (symbol != 256);
return 0;
}
static int puff_fixed(struct puff_state* s)
{
static int virgin = 1;
static short lencnt[MAXBITS + 1], lensym[FIXLCODES];
static short distcnt[MAXBITS + 1], distsym[MAXDCODES];
static struct puff_huffman lencode, distcode;
if (virgin) {
lencode.count = lencnt;
lencode.symbol = lensym;
distcode.count = distcnt;
distcode.symbol = distsym;
short lengths[FIXLCODES];
int symbol;
for (symbol = 0; symbol < 144; symbol++)
lengths[symbol] = 8;
for (; symbol < 256; symbol++)
lengths[symbol] = 9;
for (; symbol < 280; symbol++)
lengths[symbol] = 7;
for (; symbol < FIXLCODES; symbol++)
lengths[symbol] = 8;
puff_construct(&lencode, lengths, FIXLCODES);
for (symbol = 0; symbol < MAXDCODES; symbol++)
lengths[symbol] = 5;
puff_construct(&distcode, lengths, MAXDCODES);
virgin = 0;
}
return puff_codes(s, &lencode, &distcode);
}
static int puff_dynamic(struct puff_state* s)
{
static const short order[19] =
{16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
int nlen = puff_bits(s, 5) + 257;
int ndist = puff_bits(s, 5) + 1;
int ncode = puff_bits(s, 4) + 4;
if (nlen > MAXLCODES || ndist > MAXDCODES)
return -3;
short lengths[MAXCODES];
int index;
for (index = 0; index < ncode; index++)
lengths[order[index]] = puff_bits(s, 3);
for (; index < 19; index++)
lengths[order[index]] = 0;
short lencnt[MAXBITS + 1], lensym[MAXLCODES];
struct puff_huffman lencode = {lencnt, lensym};
int err = puff_construct(&lencode, lengths, 19);
if (err != 0)
return -4;
index = 0;
while (index < nlen + ndist) {
int symbol;
int len;
symbol = puff_decode(s, &lencode);
if (symbol < 0)
return symbol;
if (symbol < 16)
lengths[index++] = symbol;
else {
len = 0;
if (symbol == 16) {
if (index == 0)
return -5;
len = lengths[index - 1];
symbol = 3 + puff_bits(s, 2);
} else if (symbol == 17)
symbol = 3 + puff_bits(s, 3);
else
symbol = 11 + puff_bits(s, 7);
if (index + symbol > nlen + ndist)
return -6;
while (symbol--)
lengths[index++] = len;
}
}
if (lengths[256] == 0)
return -9;
err = puff_construct(&lencode, lengths, nlen);
if (err && (err < 0 || nlen != lencode.count[0] + lencode.count[1]))
return -7;
short distcnt[MAXBITS + 1], distsym[MAXDCODES];
struct puff_huffman distcode = {distcnt, distsym};
err = puff_construct(&distcode, lengths + nlen, ndist);
if (err && (err < 0 || ndist != distcode.count[0] + distcode.count[1]))
return -8;
return puff_codes(s, &lencode, &distcode);
}
static int puff(
unsigned char* dest,
unsigned long* destlen,
const unsigned char* source,
unsigned long sourcelen)
{
struct puff_state s = {
.out = dest,
.outlen = *destlen,
.outcnt = 0,
.in = source,
.inlen = sourcelen,
.incnt = 0,
.bitbuf = 0,
.bitcnt = 0,
};
int err;
if (setjmp(s.env) != 0)
err = 2;
else {
int last;
do {
last = puff_bits(&s, 1);
int type = puff_bits(&s, 2);
err = type == 0 ? puff_stored(&s) : (type == 1 ? puff_fixed(&s) : (type == 2 ? puff_dynamic(&s) : -1));
if (err != 0)
break;
} while (!last);
}
*destlen = s.outcnt;
return err;
}
//% END CODE DERIVED FROM puff.{c,h}
#define ZLIB_HEADER_WIDTH 2
static int puff_zlib_to_file(const unsigned char* source, unsigned long sourcelen, int dest_fd)
{
if (sourcelen < ZLIB_HEADER_WIDTH)
return 0;
source += ZLIB_HEADER_WIDTH;
sourcelen -= ZLIB_HEADER_WIDTH;
const unsigned long max_destlen = 132 << 20;
void* ret = mmap(0, max_destlen, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANON, -1, 0);
if (ret == MAP_FAILED)
return -1;
unsigned char* dest = (unsigned char*)ret;
unsigned long destlen = max_destlen;
int err = puff(dest, &destlen, source, sourcelen);
if (err) {
munmap(dest, max_destlen);
errno = -err;
return -1;
}
if (write(dest_fd, dest, destlen) != (ssize_t)destlen) {
munmap(dest, max_destlen);
return -1;
}
return munmap(dest, max_destlen);
}
static int setup_loop_device(unsigned char* data, unsigned long size, const char* loopname, int* loopfd_p)
{
int err = 0, loopfd = -1;
int memfd = syscall(__NR_memfd_create, "syzkaller", 0);
if (memfd == -1) {
err = errno;
goto error;
}
if (puff_zlib_to_file(data, size, memfd)) {
err = errno;
goto error_close_memfd;
}
loopfd = open(loopname, O_RDWR);
if (loopfd == -1) {
err = errno;
goto error_close_memfd;
}
if (ioctl(loopfd, LOOP_SET_FD, memfd)) {
if (errno != EBUSY) {
err = errno;
goto error_close_loop;
}
ioctl(loopfd, LOOP_CLR_FD, 0);
usleep(1000);
if (ioctl(loopfd, LOOP_SET_FD, memfd)) {
err = errno;
goto error_close_loop;
}
}
close(memfd);
*loopfd_p = loopfd;
return 0;
error_close_loop:
close(loopfd);
error_close_memfd:
close(memfd);
error:
errno = err;
return -1;
}
static void reset_loop_device(const char* loopname)
{
int loopfd = open(loopname, O_RDWR);
if (loopfd == -1) {
return;
}
if (ioctl(loopfd, LOOP_CLR_FD, 0)) {
}
close(loopfd);
}
static long syz_mount_image(
volatile long fsarg,
volatile long dir,
volatile long flags,
volatile long optsarg,
volatile long change_dir,
volatile unsigned long size,
volatile long image)
{
unsigned char* data = (unsigned char*)image;
int res = -1, err = 0, need_loop_device = !!size;
char* mount_opts = (char*)optsarg;
char* target = (char*)dir;
char* fs = (char*)fsarg;
char* source = NULL;
char loopname[64];
if (need_loop_device) {
int loopfd;
memset(loopname, 0, sizeof(loopname));
snprintf(loopname, sizeof(loopname), "/dev/loop%llu", procid);
if (setup_loop_device(data, size, loopname, &loopfd) == -1)
return -1;
close(loopfd);
source = loopname;
}
mkdir(target, 0777);
char opts[256];
memset(opts, 0, sizeof(opts));
if (strlen(mount_opts) > (sizeof(opts) - 32)) {
}
strncpy(opts, mount_opts, sizeof(opts) - 32);
if (strcmp(fs, "iso9660") == 0) {
flags |= MS_RDONLY;
} else if (strncmp(fs, "ext", 3) == 0) {
bool has_remount_ro = false;
char* remount_ro_start = strstr(opts, "errors=remount-ro");
if (remount_ro_start != NULL) {
char after = *(remount_ro_start + strlen("errors=remount-ro"));
char before = remount_ro_start == opts ? '\0' : *(remount_ro_start - 1);
has_remount_ro = ((before == '\0' || before == ',') && (after == '\0' || after == ','));
}
if (strstr(opts, "errors=panic") || !has_remount_ro)
strcat(opts, ",errors=continue");
} else if (strcmp(fs, "xfs") == 0) {
strcat(opts, ",nouuid");
} else if (strncmp(fs, "gfs2", 4) == 0 && (strstr(opts, "errors=panic") || strstr(opts, "debug"))) {
strcat(opts, ",errors=withdraw");
}
res = mount(source, target, fs, flags, opts);
if (res == -1) {
err = errno;
goto error_clear_loop;
}
res = open(target, O_RDONLY | O_DIRECTORY);
if (res == -1) {
err = errno;
goto error_clear_loop;
}
if (change_dir) {
res = chdir(target);
if (res == -1) {
err = errno;
}
}
error_clear_loop:
if (need_loop_device)
reset_loop_device(loopname);
errno = err;
return res;
}
uint64_t r[1] = {0xffffffffffffffff};
int main(void)
{
syscall(__NR_mmap, /*addr=*/0x1ffffffff000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/(intptr_t)-1, /*offset=*/0ul);
syscall(__NR_mmap, /*addr=*/0x200000000000ul, /*len=*/0x1000000ul, /*prot=PROT_WRITE|PROT_READ|PROT_EXEC*/7ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/(intptr_t)-1, /*offset=*/0ul);
syscall(__NR_mmap, /*addr=*/0x200001000000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/(intptr_t)-1, /*offset=*/0ul);
const char* reason;
(void)reason;
intptr_t res = 0;
if (write(1, "executing program\n", sizeof("executing program\n") - 1)) {}
// openat$ttyS3 arguments: [
// fd: const = 0xffffffffffffff9c (8 bytes)
// file: ptr[in, buffer] {
// buffer: {2f 64 65 76 2f 74 74 79 53 33 00} (length 0xb)
// }
// flags: open_flags = 0x0 (4 bytes)
// mode: const = 0x0 (2 bytes)
// ]
// returns fd_tty
memcpy((void*)0x200000000080, "/dev/ttyS3\000", 11);
res = syscall(__NR_openat, /*fd=*/0xffffffffffffff9cul, /*file=*/0x200000000080ul, /*flags=*/0, /*mode=*/0);
if (res != -1)
r[0] = res;
// ioctl$TIOCSETD arguments: [
// fd: fd_tty (resource)
// cmd: const = 0x5423 (4 bytes)
// arg: ptr[in, int32] {
// int32 = 0x14 (4 bytes)
// }
// ]
*(uint32_t*)0x200000000040 = 0x14;
syscall(__NR_ioctl, /*fd=*/r[0], /*cmd=*/0x5423, /*arg=*/0x200000000040ul);
// syz_mount_image$ocfs2 arguments: [
// fs: ptr[in, buffer] {
// buffer: {6f 63 66 73 32 00} (length 0x6)
// }
// dir: ptr[in, buffer] {
// buffer: {2e 2f 66 69 6c 65 31 00} (length 0x8)
// }
// flags: mount_flags = 0x8c0 (8 bytes)
// opts: ptr[inout, array[ANYUNION]] {
// array[ANYUNION] {
// union ANYUNION {
// ANYBLOB: buffer: {61 63 6c 2c 68 65 61 72 74 62 65 61 74 3d 6e 6f 6e 65 2c 65 72 72 6f 72 73 3d 72 65 6d 6f 75 6e 74 2d 72 6f 2c 63 6f 68 65 72 65 6e 63 79 3d 66 75 6c 6c 2c 63 6f 68 65 72 65 6e 63 79 3d 66 75 6c 6c 2c 6c 6f 63 61 6c 66 6c 6f 63 6b 73 2c 69 6e 74 72 2c 6e 6f 61 63 6c 2c 00 19 67 b9 b8 a6 cd d6 36 d7 54 28 f2 c5 e8 05 4d 01 85 8e ef 55 27 55 57 6e 74 95 26 b3 68 60 cf 25 11 04 0d 1c e5 a7 43 ff d8 3d 29 d1 ba 3a 54 a5 9d 8c 7a a2 49 f0 8d 3c 8c 6d 04 ac 10 5d 67 93 4d b6 19 0d 59 f2 32 3b 55 a5 a4} (length 0xa7)
// }
// }
// }
// chdir: int8 = 0x1 (1 bytes)
// size: len = 0x442a (8 bytes)
// img: ptr[in, buffer] {
// buffer: (compressed buffer with length 0x442a)
// }
// ]
// returns fd_dir
memcpy((void*)0x200000004440, "ocfs2\000", 6);
memcpy((void*)0x200000000040, "./file1\000", 8);
memcpy((void*)0x200000000100, "... [truncated large byte array] ...", 167);
memcpy((void*)0x200000008940, "... [truncated large byte array] ...", 17450);
syz_mount_image(/*fs=*/0x200000004440, /*dir=*/0x200000000040, /*flags=MS_NODIRATIME|MS_MANDLOCK|MS_DIRSYNC*/0x8c0, /*opts=*/0x200000000100, /*chdir=*/1, /*size=*/0x442a, /*img=*/0x200000008940);
return 0;
}
Reply: **Bug Analysis:**
The bug is an infinite loop in `handle_tx()` within `drivers/net/caif/caif_serial.c`, which leads to an RCU stall and soft lockup.
Here is the sequence of events that leads to the bug:
1. A privileged user opens a serial port (e.g., `/dev/ttyS3`) and attaches the `N_CAIF` line discipline to it via `ioctl(TIOCSETD)`. This creates a `caif` network device.
2. The user closes the serial port. During the TTY teardown process, `tty_port_shutdown()` is called, which invokes `uart_free_xmit_buf()`.
3. `uart_free_xmit_buf()` frees the UART transmit buffer (`xmit_buf = NULL`) and re-initializes the transmit FIFO (`INIT_KFIFO(port->xmit_fifo)`).
4. Because the FIFO is re-initialized (its mask is 0), `kfifo_avail()` incorrectly returns `1`. Consequently, `uart_write_room()` also returns `1`.
5. There is a race window where the TTY's `xmit_buf` is freed, but the `caif` network device is still registered and up (it is unregistered asynchronously via a workqueue in `ser_release()`).
6. If a packet is transmitted over the `caif` network device during this window (in the reproducer, this is triggered by `aoe` broadcasting discovery packets or `ocfs2` heartbeat traffic), the network stack calls the device's `ndo_start_xmit`, which maps to `caif_xmit()` and then `handle_tx()`.
7. `handle_tx()` checks `tty_write_room()`, which returns `1`. It then attempts to write 1 byte using `tty->ops->write()` (which maps to `uart_write()`).
8. Because `xmit_buf` is `NULL`, `uart_write()` immediately returns `0`.
9. `handle_tx()` sees that `0` bytes were written, does not consume any data from the `skb`, and loops again. It repeatedly gets `1` from `tty_write_room()` and `0` from `uart_write()`, resulting in an infinite loop.
10. Since `ndo_start_xmit` is called with bottom halves disabled (or under a spinlock), this infinite loop causes an RCU stall and soft lockup.
**Security Impact Assessment:**
* **Exploitable:** **False**. The bug is a pure infinite loop in the kernel control flow. There is no memory corruption, use-after-free, or out-of-bounds access involved. It cannot be exploited for privilege escalation or arbitrary code execution.
* **Denial Of Service:** **True**. The infinite loop causes an RCU stall and soft lockup, which hangs the CPU core and leads to a system crash or freeze.
* **Accessible From Unprivileged Processes:** **False**. Attaching the `N_CAIF` line discipline requires `CAP_SYS_ADMIN` or `CAP_SYS_TTY_CONFIG` privileges. This is explicitly checked in `ldisc_open()` in `caif_serial.c`. Unprivileged users cannot set up the vulnerable state.
* **Accessible From User Namespaces:** **False**. The capability check in `ldisc_open()` uses `capable()`, which checks for the capability in the initial (global) user namespace. Therefore, even a root user inside a user namespace cannot trigger this bug.
* **Network / Remote / Peripheral / Filesystem Trigger:** **False**. The bug is triggered by local network transmission (TX path) during a specific race window on a locally configured TTY. While the reproducer uses an `ocfs2` filesystem mount, it is merely a side-effect to generate local network traffic (via `aoe` or cluster heartbeats) and not a vulnerability in the filesystem parsing itself.
|
| 6/2 |
2026/05/23 09:43 |
llm |
expert |
0m
Model:
Tokens:
input: 16431
output: 45
thoughts: 1196
Thoughts: **RCU Stall Investigation: A Deep Dive into AOE, CAIF, and Lock Contention**
Okay, so we've got an RCU stall report, and it's on CPU 0. Let's dig in. The stack trace on CPU 0 shows a kthread named `aoe_tx0` that seems to be the culprit. It looks like we're in `__raw_spin_unlock_irqrestore` and then `_raw_spin_unlock_irqrestore`, so there might be an issue with spinlock usage. The trace points through serial core functions, and then into `caif_serial`, and finally the `aoe` block driver.
The reproducer is doing something interesting: it opens `/dev/ttyS3`, attaches the `N_CAIF` line discipline to it, and *then* mounts an `ocfs2` image. Hmm, could there be an interaction between these? It seems `ocfs2` doesn't directly use `aoe`, so the assumption of `ocfs2` using `aoe` is incorrect here. It seems more like the reproducer is designed to trigger communication through `aoe`.
The important thing is that `aoe` is sending packets and we're seeing an RCU stall while the `aoe` driver is active. This `aoe` driver's responsibility is sending packets over a network. Now I remember, `aoe` broadcasts packets over *all* network interfaces. If that interface happens to be a `caif` serial device, as in this case, then `dev_queue_xmit` will be called on it, triggering the `caif_serial` driver's `ndo_start_xmit` function, which is `caif_xmit`. `caif_xmit` will then call `handle_tx`. It seems we need to examine `handle_tx` in `drivers/net/caif/caif_serial.c` to understand the lock contention and pinpoint the cause of this stall. This looks like a potential lock contention issue between the `aoe` driver's broadcast behavior and the `caif_serial` driver's locking.
|
| 7/2 |
2026/05/23 09:43 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/caif/caif_serial.c IncludeLines:true Name:handle_tx]
Results: map[SourceCode: 194: static int handle_tx(struct ser_device *ser)
195: {
196: struct tty_struct *tty;
197: struct sk_buff *skb;
198: int tty_wr, len, room;
199:
200: tty = ser->tty;
201: ser->tx_started = true;
202:
203: /* Enter critical section */
204: if (test_and_set_bit(CAIF_SENDING, &ser->state))
205: return 0;
206:
207: /* skb_peek is safe because handle_tx is called after skb_queue_tail */
208: while ((skb = skb_peek(&ser->head)) != NULL) {
209:
210: /* Make sure you don't write too much */
211: len = skb->len;
212: room = tty_write_room(tty);
213: if (!room)
214: break;
215: if (room > ser_write_chunk)
216: room = ser_write_chunk;
217: if (len > room)
218: len = room;
219:
220: /* Write to tty or loopback */
221: if (!ser_loop) {
222: tty_wr = tty->ops->write(tty, skb->data, len);
223: update_tty_status(ser);
224: } else {
225: tty_wr = len;
226: ldisc_receive(tty, skb->data, NULL, len);
227: }
228: ser->dev->stats.tx_packets++;
229: ser->dev->stats.tx_bytes += tty_wr;
230:
231: /* Error on TTY ?! */
232: if (tty_wr < 0)
233: goto error;
234: /* Reduce buffer written, and discard if empty */
235: skb_pull(skb, tty_wr);
236: if (skb->len == 0) {
237: struct sk_buff *tmp = skb_dequeue(&ser->head);
238: WARN_ON(tmp != skb);
239: dev_consume_skb_any(skb);
240: }
241: }
242: /* Send flow off if queue is empty */
243: if (ser->head.qlen <= SEND_QUEUE_LOW &&
244: test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) &&
245: ser->common.flowctrl != NULL)
246: ser->common.flowctrl(ser->dev, ON);
247: clear_bit(CAIF_SENDING, &ser->state);
248: return 0;
249: error:
250: clear_bit(CAIF_SENDING, &ser->state);
251: return tty_wr;
252: }
SourceFile:drivers/net/caif/caif_serial.c]
|
| 8/2 |
2026/05/23 09:43 |
llm |
expert |
0m
Model:
Tokens:
input: 19079
output: 45
thoughts: 72
Thoughts: **Debugging a Write Stall**
Okay, so I'm seeing a stall, and it looks like the issue is originating within `uart_write_room`. Right, and that function is called from `tty_write_room(tty)`. Okay, that's a key bit of the puzzle, so I'll follow that chain. Now, let me see... `tty_write_room` has to be calling the TTY's specific write room function, which is done through `tty->ops->write_room(tty)`. Excellent, that makes sense. So, `uart_write_room` must be the *implementation* for that specific UART. Let me double-check that by heading over to `drivers/tty/serial/serial_core.c` and take a look at the code for `uart_write_room`. Hopefully, this will lead me to the root cause of this stalling behavior.
|
| 9/2 |
2026/05/23 09:43 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/serial/serial_core.c IncludeLines:true Name:uart_write_room]
Results: map[SourceCode: 638: static unsigned int uart_write_room(struct tty_struct *tty)
639: {
640: struct uart_state *state = tty->driver_data;
641: struct uart_port *port;
642: unsigned long flags;
643: unsigned int ret;
644:
645: port = uart_port_ref_lock(state, &flags);
646: ret = kfifo_avail(&state->port.xmit_fifo);
647: uart_port_unlock_deref(port, flags);
648: return ret;
649: }
SourceFile:drivers/tty/serial/serial_core.c]
|
| 10/2 |
2026/05/23 09:43 |
llm |
expert |
0m
Model:
Tokens:
input: 19603
output: 43
thoughts: 526
Thoughts: **Analyzing a Potential UART TX Loop**
Okay, so I'm thinking about this `uart_port_ref_lock` and how it's used with a spinlock. If the `handle_tx` function gets stuck in an infinite loop, that spinlock could be held and released repeatedly, or worse, it might just hog the CPU without yielding, right? Let's take another look at the `handle_tx` code block to confirm this.
I see it iterates through a queue of SKBs (Socket Buffers) using `skb_peek` and `skb_dequeue`. It calculates the amount of data it can write (`len`) based on the SKB's size and the available space on the TTY (`room`). If there's enough room, it writes to the TTY using `tty->ops->write`. It updates statistics and then pulls the written bytes from the SKB using `skb_pull`. If the SKB is now empty, it deallocates it. The core of my concern focuses on the condition when `tty->ops->write` returns zero.
Now, if `tty_wr` is zero, `skb_pull` with an argument of zero does nothing. This means the `skb->len` doesn't change from the original `len`, provided `len > 0`. The loop continues, and `skb_peek` will return the same SKB again, unless the buffer is consumed elsewhere. If `room` is still greater than zero, the code will *attempt* to write the data again. Here's the catch: *if* `tty->ops->write` returns zero persistently, we've got an infinite loop on our hands. The code will keep trying to write, but nothing will be consumed. So, it's looping.
I need to confirm if `tty->ops->write` *can* return zero and what that would mean. Let's dig into the `uart_write` function in `serial_core.c` to understand the TTY write behavior better and see if this is even a realistic scenario.
|
| 11/2 |
2026/05/23 09:43 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/serial/serial_core.c IncludeLines:true Name:uart_write]
Results: map[SourceCode: 610: static ssize_t uart_write(struct tty_struct *tty, const u8 *buf, size_t count)
611: {
612: struct uart_state *state = tty->driver_data;
613: struct uart_port *port;
614: unsigned long flags;
615: int ret = 0;
616:
617: /*
618: * This means you called this function _after_ the port was
619: * closed. No cookie for you.
620: */
621: if (WARN_ON(!state))
622: return -EL3HLT;
623:
624: port = uart_port_ref_lock(state, &flags);
625: if (!state->port.xmit_buf) {
626: uart_port_unlock_deref(port, flags);
627: return 0;
628: }
629:
630: if (port)
631: ret = kfifo_in(&state->port.xmit_fifo, buf, count);
632:
633: __uart_start(state);
634: uart_port_unlock_deref(port, flags);
635: return ret;
636: }
SourceFile:drivers/tty/serial/serial_core.c]
|
| 12/2 |
2026/05/23 09:43 |
llm |
expert |
0m
Model:
Tokens:
input: 21033
output: 41
thoughts: 528
Thoughts: **Analyzing the UART Write Path and FIFO Availability**
Okay, so I'm looking at this `uart_write` function, and it seems like if `state->port.xmit_buf` is NULL, the function returns 0. That's fine, expected behavior. But hold on, `uart_write_room` is being used to determine how much space is available. And `uart_write_room` relies on `kfifo_avail(&state->port.xmit_fifo)`. The question then becomes, what does `kfifo_avail` return when `state->port.xmit_buf` is NULL?
Let's dissect `kfifo_avail`. Itβs returning `fifo->kfifo.mask + 1 - fifo->kfifo.in + fifo->kfifo.out`. Now, if `xmit_buf` is NULL, does that mean the FIFO is uninitialized? When is this buffer actually allocated? Ah, yes, in `uart_port_startup`. So, if the port isn't fully initialized, or maybe if it's been shut down, `xmit_buf` *could* be NULL. But `uart_write_room` doesn't explicitly check for this NULL condition, it just calls `kfifo_avail`. Let's re-examine `uart_write_room`:
```c
static unsigned int uart_write_room(struct tty_struct *tty)
{
struct uart_state *state = tty->driver_data;
struct uart_port *port;
unsigned long flags;
unsigned int ret;
port = uart_port_ref_lock(state, &flags);
ret = kfifo_avail(&state->port.xmit_fifo);
uart_port_unlock_deref(port, flags);
return ret;
}
```
Okay, so the `uart_write_room` function doesn't seem to account for a NULL `xmit_buf`. So, if `xmit_buf` is NULL, `kfifo_avail` *could* return 0, or it might return some positive value depending on the state of the FIFO structure.
Wait a second. The `kfifo` itself is initialized in `uart_port_startup`, via `kfifo_alloc`:
```c
retval = kfifo_alloc(&state->port.xmit_fifo, PAGE_SIZE, GFP_KERNEL);
```
If `xmit_buf` is NULL, then either `kfifo_alloc` hasn't been called, or `kfifo_free` has been. If `kfifo_free` has been called, the `fifo->kfifo.mask` is 0. So, `kfifo_avail` would return 0, right? Hmm, no, let's look at `kfifo_avail` again, it's `fifo->kfifo.mask + 1 - (in - out)`. If `mask` is 0, and *both* `in` and `out` are 0, it *would* return 1! This seems counter-intuitive. I need to double-check the `kfifo_avail` implementation to confirm this behavior.
|
| 13/2 |
2026/05/23 09:44 |
tool |
codesearch-definition-source |
0m
Error:
Args: map[ContextFile:include/linux/kfifo.h IncludeLines:true Name:kfifo_avail]
Results: map[SourceCode: SourceFile:]
|
| 14/2 |
2026/05/23 09:44 |
llm |
expert |
0m
Model:
Tokens:
input: 22326
output: 19
thoughts: 14
Thoughts: Okay, here's my summary, presented as a stream of thought:
**Identifying the Beast**
Right, so I'm looking at this... immediately, the structure screams "macro." Not a complex algorithm, more of a pre-processor directive. Okay, good start. Now the hunt begins. Need to *find* the damn thing, right? Where is it lurking in the code? Is it defined inline, pulled in from a header, a pre-compiled library? Gotta trace this down to understand its purpose. This is the first, crucial step. Let's see...
|
| 15/2 |
2026/05/23 09:44 |
tool |
grepper |
0m
Error:
Args: map[Expression:define kfifo_avail]
Results:
|
| 16/2 |
2026/05/23 09:44 |
llm |
expert |
0m
Model:
Tokens:
input: 22495
output: 18
thoughts: 22
Thoughts: Here's my thought process, summarized as you requested:
**Investigating Kernel FIFO Availability**
Okay, let's dive into this. I need to understand how available space is calculated within a kernel FIFO. The obvious place to start is the header file where the kfifo structure itself is defined. That would be `include/linux/kfifo.h`. I'll be looking for a function or variable specifically related to checking or calculating the available space within the FIFO β something named, perhaps, `kfifo_avail`. It's likely a macro or inline function. Time to see what's in there.
|
| 17/2 |
2026/05/23 09:44 |
tool |
grepper |
0m
Args: map[Expression:kfifo_avail]
Results: map[Output:arch/powerpc/sysdev/fsl_rmu.c=388=fsl_rio_port_write_handler(int irq, void *dev_instance)
--
arch/powerpc/sysdev/fsl_rmu.c-419- */
arch/powerpc/sysdev/fsl_rmu.c:420: if (kfifo_avail(&pw->pw_fifo) >= RIO_PW_MSG_SIZE) {
arch/powerpc/sysdev/fsl_rmu.c-421- pw->port_write_msg.msg_count++;
--
arch/x86/kvm/hyperv.c=1933=static void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu,
--
arch/x86/kvm/hyperv.c-1949- */
arch/x86/kvm/hyperv.c:1950: if (count && entries && count < kfifo_avail(&tlb_flush_fifo->entries)) {
arch/x86/kvm/hyperv.c-1951- WARN_ON(kfifo_in(&tlb_flush_fifo->entries, entries, count) != count);
--
drivers/crypto/hisilicon/sec/sec_algs.c=421=static void sec_skcipher_alg_callback(struct sec_bd_info *sec_resp,
--
drivers/crypto/hisilicon/sec/sec_algs.c-503- (ctx->queue->havesoftqueue &&
drivers/crypto/hisilicon/sec/sec_algs.c:504: kfifo_avail(&ctx->queue->softqueue) >
drivers/crypto/hisilicon/sec/sec_algs.c-505- backlog_req->num_elements)) {
--
drivers/crypto/hisilicon/sec/sec_algs.c=707=static int sec_alg_skcipher_crypto(struct skcipher_request *skreq,
--
drivers/crypto/hisilicon/sec/sec_algs.c-811- (!queue->havesoftqueue ||
drivers/crypto/hisilicon/sec/sec_algs.c:812: kfifo_avail(&queue->softqueue) > steps)) ||
drivers/crypto/hisilicon/sec/sec_algs.c-813- !list_empty(&ctx->backlog)) {
--
drivers/firmware/arm_scmi/notify.c=583=int scmi_notify(const struct scmi_handle *handle, u8 proto_id, u8 evt_id,
--
drivers/firmware/arm_scmi/notify.c-601- }
drivers/firmware/arm_scmi/notify.c:602: if (kfifo_avail(&r_evt->proto->equeue.kfifo) < sizeof(eh) + len) {
drivers/firmware/arm_scmi/notify.c-603- dev_warn(handle->dev,
--
drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c=174=static void add_event_to_kfifo(pid_t pid, struct kfd_node *dev,
--
drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c-184- spin_lock(&client->lock);
drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c:185: if (kfifo_avail(&client->fifo) >= len) {
drivers/gpu/drm/amd/amdkfd/kfd_smi_events.c-186- kfifo_in(&client->fifo, event_msg, len);
--
drivers/hid/hid-sensor-custom.c=416=static int hid_sensor_capture_sample(struct hid_sensor_hub_device *hsdev,
--
drivers/hid/hid-sensor-custom.c-441- header.timestamp = ktime_get_real_ns();
drivers/hid/hid-sensor-custom.c:442: if (kfifo_avail(&sensor_inst->data_fifo) >= required_size) {
drivers/hid/hid-sensor-custom.c-443- kfifo_in(&sensor_inst->data_fifo,
--
drivers/hid/hid-sensor-custom.c-448- }
drivers/hid/hid-sensor-custom.c:449: if (kfifo_avail(&sensor_inst->data_fifo) >= raw_len)
drivers/hid/hid-sensor-custom.c-450- kfifo_in(&sensor_inst->data_fifo, (unsigned char *)raw_data,
--
drivers/hid/wacom_sys.c=51=static void wacom_wac_queue_insert(struct hid_device *hdev,
--
drivers/hid/wacom_sys.c-56-
drivers/hid/wacom_sys.c:57: while (kfifo_avail(fifo) < size) {
drivers/hid/wacom_sys.c-58- if (!warned)
--
drivers/iio/buffer/kfifo_buf.c=141=static size_t iio_kfifo_buf_space_available(struct iio_buffer *r)
--
drivers/iio/buffer/kfifo_buf.c-146- mutex_lock(&kf->user_lock);
drivers/iio/buffer/kfifo_buf.c:147: avail = kfifo_avail(&kf->kf);
drivers/iio/buffer/kfifo_buf.c-148- mutex_unlock(&kf->user_lock);
--
drivers/platform/surface/surface_aggregator_cdev.c=93=static u32 ssam_cdev_notifier(struct ssam_event_notifier *nf, const struct ssam_event *in)
--
drivers/platform/surface/surface_aggregator_cdev.c-109- /* Make sure we have enough space. */
drivers/platform/surface/surface_aggregator_cdev.c:110: if (kfifo_avail(&client->buffer) < n) {
drivers/platform/surface/surface_aggregator_cdev.c-111- dev_warn(client->cdev->dev,
--
drivers/platform/surface/surface_dtx.c=596=static void sdtx_push_event(struct sdtx_device *ddev, struct sdtx_event *evt)
--
drivers/platform/surface/surface_dtx.c-607-
drivers/platform/surface/surface_dtx.c:608: if (likely(kfifo_avail(&client->buffer) >= len))
drivers/platform/surface/surface_dtx.c-609- kfifo_in(&client->buffer, (const u8 *)evt, len);
--
drivers/rapidio/devices/rio_mport_cdev.c=1355=static int rio_mport_add_event(struct mport_cdev_priv *priv,
--
drivers/rapidio/devices/rio_mport_cdev.c-1363- spin_lock(&priv->fifo_lock);
drivers/rapidio/devices/rio_mport_cdev.c:1364: overflow = kfifo_avail(&priv->event_fifo) < sizeof(*event)
drivers/rapidio/devices/rio_mport_cdev.c-1365- || kfifo_in(&priv->event_fifo, (unsigned char *)event,
--
drivers/rapidio/devices/tsi721.c=259=tsi721_pw_handler(struct tsi721_device *priv)
--
drivers/rapidio/devices/tsi721.c-276- spin_lock(&priv->pw_fifo_lock);
drivers/rapidio/devices/tsi721.c:277: if (kfifo_avail(&priv->pw_fifo) >= TSI721_RIO_PW_MSG_SIZE)
drivers/rapidio/devices/tsi721.c-278- kfifo_in(&priv->pw_fifo, pw_buf,
--
drivers/staging/greybus/uart.c=442=static unsigned int gb_tty_write_room(struct tty_struct *tty)
--
drivers/staging/greybus/uart.c-448- spin_lock_irqsave(&gb_tty->write_lock, flags);
drivers/staging/greybus/uart.c:449: room = kfifo_avail(&gb_tty->write_fifo);
drivers/staging/greybus/uart.c-450- spin_unlock_irqrestore(&gb_tty->write_lock, flags);
--
drivers/tty/mxser.c=928=static unsigned int mxser_write_room(struct tty_struct *tty)
--
drivers/tty/mxser.c-931-
drivers/tty/mxser.c:932: return kfifo_avail(&info->port.xmit_fifo);
drivers/tty/mxser.c-933-}
--
drivers/tty/n_gsm.c=4414=static unsigned int gsmtty_write_room(struct tty_struct *tty)
--
drivers/tty/n_gsm.c-4418- return 0;
drivers/tty/n_gsm.c:4419: return kfifo_avail(&dlci->fifo);
drivers/tty/n_gsm.c-4420-}
--
drivers/tty/nozomi.c=1623=static unsigned int ntty_write_room(struct tty_struct *tty)
--
drivers/tty/nozomi.c-1629- if (dc)
drivers/tty/nozomi.c:1630: room = kfifo_avail(&port->fifo_ul);
drivers/tty/nozomi.c-1631-
--
drivers/tty/serial/serial_core.c=638=static unsigned int uart_write_room(struct tty_struct *tty)
--
drivers/tty/serial/serial_core.c-645- port = uart_port_ref_lock(state, &flags);
drivers/tty/serial/serial_core.c:646: ret = kfifo_avail(&state->port.xmit_fifo);
drivers/tty/serial/serial_core.c-647- uart_port_unlock_deref(port, flags);
--
drivers/usb/gadget/function/f_midi.c=364=static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
--
drivers/usb/gadget/function/f_midi.c-382- /* pre-allocate write usb requests to use on f_midi_transmit. */
drivers/usb/gadget/function/f_midi.c:383: while (kfifo_avail(&midi->in_req_fifo)) {
drivers/usb/gadget/function/f_midi.c-384- struct usb_request *req =
--
drivers/usb/gadget/function/u_serial.c=825=static unsigned int gs_write_room(struct tty_struct *tty)
--
drivers/usb/gadget/function/u_serial.c-832- if (port->port_usb)
drivers/usb/gadget/function/u_serial.c:833: room = kfifo_avail(&port->port_write_buf);
drivers/usb/gadget/function/u_serial.c-834- spin_unlock_irqrestore(&port->port_lock, flags);
--
drivers/usb/host/xhci-dbgtty.c=351=static unsigned int dbc_tty_write_room(struct tty_struct *tty)
--
drivers/usb/host/xhci-dbgtty.c-357- spin_lock_irqsave(&port->port_lock, flags);
drivers/usb/host/xhci-dbgtty.c:358: room = kfifo_avail(&port->port.xmit_fifo);
drivers/usb/host/xhci-dbgtty.c-359-
--
drivers/usb/serial/cypress_m8.c=790=static unsigned int cypress_write_room(struct tty_struct *tty)
--
drivers/usb/serial/cypress_m8.c-797- spin_lock_irqsave(&priv->lock, flags);
drivers/usb/serial/cypress_m8.c:798: room = kfifo_avail(&priv->write_fifo);
drivers/usb/serial/cypress_m8.c-799- spin_unlock_irqrestore(&priv->lock, flags);
--
drivers/usb/serial/generic.c=232=unsigned int usb_serial_generic_write_room(struct tty_struct *tty)
--
drivers/usb/serial/generic.c-241- spin_lock_irqsave(&port->lock, flags);
drivers/usb/serial/generic.c:242: room = kfifo_avail(&port->write_fifo);
drivers/usb/serial/generic.c-243- spin_unlock_irqrestore(&port->lock, flags);
--
drivers/usb/serial/io_ti.c=2073=static unsigned int edge_write_room(struct tty_struct *tty)
--
drivers/usb/serial/io_ti.c-2085- spin_lock_irqsave(&edge_port->ep_lock, flags);
drivers/usb/serial/io_ti.c:2086: room = kfifo_avail(&port->write_fifo);
drivers/usb/serial/io_ti.c-2087- spin_unlock_irqrestore(&edge_port->ep_lock, flags);
--
drivers/usb/serial/oti6858.c=366=static unsigned int oti6858_write_room(struct tty_struct *tty)
--
drivers/usb/serial/oti6858.c-372- spin_lock_irqsave(&port->lock, flags);
drivers/usb/serial/oti6858.c:373: room = kfifo_avail(&port->write_fifo);
drivers/usb/serial/oti6858.c-374- spin_unlock_irqrestore(&port->lock, flags);
--
drivers/usb/serial/ti_usb_3410_5052.c=810=static unsigned int ti_write_room(struct tty_struct *tty)
--
drivers/usb/serial/ti_usb_3410_5052.c-817- spin_lock_irqsave(&tport->tp_lock, flags);
drivers/usb/serial/ti_usb_3410_5052.c:818: room = kfifo_avail(&port->write_fifo);
drivers/usb/serial/ti_usb_3410_5052.c-819- spin_unlock_irqrestore(&tport->tp_lock, flags);
--
include/linux/kfifo.h=174=__kfifo_int_must_check_helper(int val)
--
include/linux/kfifo.h-295-/**
include/linux/kfifo.h:296: * kfifo_avail - returns the number of unused elements in the fifo
include/linux/kfifo.h-297- * @fifo: address of the fifo to be used
include/linux/kfifo.h-298- */
include/linux/kfifo.h:299:#define kfifo_avail(fifo) \
include/linux/kfifo.h-300-__kfifo_uint_must_check_helper( \
--
sound/soc/intel/avs/debugfs.c=19=static unsigned int __kfifo_fromio(struct kfifo *fifo, const void __iomem *src, unsigned int len)
--
sound/soc/intel/avs/debugfs.c-23-
sound/soc/intel/avs/debugfs.c:24: len = min(len, kfifo_avail(fifo));
sound/soc/intel/avs/debugfs.c-25- off = __fifo->in & __fifo->mask;
--
sound/usb/line6/driver.c=647=static void line6_hwdep_push_message(struct usb_line6 *line6)
--
sound/usb/line6/driver.c-651-
sound/usb/line6/driver.c:652: if (kfifo_avail(&line6->messages.fifo) >= line6->message_length) {
sound/usb/line6/driver.c-653- /* No race condition here, there's only one writer */
]
|
| 18/2 |
2026/05/23 09:44 |
llm |
expert |
1m
Model:
Tokens:
input: 26874
output: 41
thoughts: 22
Thoughts: Here's my take on the thought process, as requested:
**Diving into the `kfifo_avail` Macro**
Okay, time to get my hands dirty. I need to understand how the available space calculation works for these kernel FIFOs, so I'm going to jump straight into the source. Let's see... the `kfifo_avail` macro should be defined in `include/linux/kfifo.h`. That's the logical place to start β good code should be well-organized, and the headers are where you expect the core definitions to live. I'm going to pull up that file and immediately look for `kfifo_avail`. I'm expecting some clever bitwise magic or modulo arithmetic, given the circular buffer nature of a FIFO. I want to see how they're handling wraparound and calculating the available space efficiently. I'm hoping it's straightforward but elegant β no complex constructs, just clean, performant code. Let's get to it.
|
| 19/2 |
2026/05/23 09:45 |
tool |
codesearch-definition-source |
0m
Error:
Args: map[ContextFile:include/linux/kfifo.h IncludeLines:true Name:kfifo_avail]
Results: map[SourceCode: SourceFile:]
|
| 20/2 |
2026/05/23 09:45 |
llm |
expert |
0m
Model:
Tokens:
input: 27169
output: 19
thoughts: 46
Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience:
**Investigating a Possible Macro and Its Definition**
Right, this looks like it's pointing me at a macro. The concern, as always, is that a simple `codesearch-definition-source` might not pick it up if it's a macro and not a function. So, best practice is to manually inspect the source. I'm going to start with `include/linux/kfifo.h`, specifically around line 299. That's usually a good place to start when dealing with a kernel data structure like `kfifo`. Time to dig in and see what's actually going on there; I'm expecting something along the lines of a macro definition, which hopefully is relatively straightforward to decipher.
|
| 21/2 |
2026/05/23 09:45 |
tool |
grepper |
0m
Error:
Args: map[Expression:define kfifo_avail]
Results:
|
| 22/2 |
2026/05/23 09:45 |
llm |
expert |
0m
Model:
Tokens:
input: 27418
output: 48
thoughts: 731
Thoughts: **Analyzing a Potential Infinite Loop in CAIF Serial Driver**
Okay, I've got this section of code in front of me, and I'm seeing a potential infinite loop within the `caif_serial.c` driver. It starts with this `kfifo_avail` call, which, as I look at it, seems like it could return an unexpected value, specifically "1," if the underlying kfifo has been freed or never allocated. And I've seen that behavior before.
Digging deeper, it traces to `uart_write_room` returning 1. This value feeds into the `handle_tx` function. The key here is that `tty->ops->write`, which in this case is `uart_write`, is returning 0. Why? I see that `uart_write` will return 0 if the `xmit_buf` is NULL, and I remember `xmit_buf` is allocated in the tty open routine `uart_port_startup` and deallocated at close `uart_port_shutdown`.
The result of that is that `tty_wr` is assigned a 0, the skb length isn't changed and the loop continues.
This keeps looping.
The issue then is that `xmit_buf` is NULL. That seems like a race condition: the TTY must have been closed, and `uart_port_shutdown` called, setting `xmit_buf` to NULL. But the CAIF network device is still trying to write to the tty. The `caif` network device is created when `ioctl(fd, TIOCSETD, N_CAIF)` is called. If the tty is closed, then the line discipline should close, which should de-register the network device or at least stop it!
I need to trace the `caif_tty_close` function to confirm whether or not this is the case.
|
| 23/2 |
2026/05/23 09:45 |
tool |
codesearch-definition-source |
0m
Error:
Args: map[ContextFile:drivers/net/caif/caif_serial.c IncludeLines:true Name:caif_tty_close]
Results: map[SourceCode: SourceFile:]
|
| 24/2 |
2026/05/23 09:45 |
llm |
expert |
0m
Model:
Tokens:
input: 28624
output: 32
thoughts: 23
Thoughts: Okay, let's dive into this. Here's how I'd approach summarizing the prompt, keeping in mind my own expert-level perspective:
**Diving into `caif_serial.c`**
Alright, so the task at hand is to understand the core functions within `drivers/net/caif/caif_serial.c`. Given that I'm dealing with the CAIF (Common Abstraction for Interconnect Framework) driver and specifically the serial implementation, I immediately know this file is going to contain the glue code for using a serial port (likely UART) as a CAIF transport. This implies functions for initialization, de-initialization, sending and receiving data frames, and potentially handling flow control. My first thought is to quickly identify the key functional blocks. I will be looking for:
* **Initialization and De-initialization:** The `module_init` and `module_exit` macros would be a quick way to find the primary initialization and cleanup functions of the module.
* **Device Structure Handling:** `struct caif_dev` and `struct serial_port` will definitely be at the center of the structure, and I'll need to know what structures the module makes use of.
* **Transmit and Receive Handlers:** I'll be looking for functions that handle the actual data transfer to and from the serial port. These likely interface with the underlying serial driver (e.g., via `tty` or direct hardware access, depending on the architecture).
* **Interrupt Handling:** Serial communication frequently relies on interrupts for receiving data. I'll need to know where and how the interrupt handler is set up and what it does.
* **Error Handling:** The implementation of the serial CAIF transport also needs to account for error conditions. Functions or mechanisms for handling serial errors like framing errors, parity errors, and overrun/underrun conditions will be relevant.
* **Flow Control:** The serial port's flow control methods will have to be examined.
My immediate goal is to get a general outline of the code's structure and major functions. Then, I can delve into the details of specific functions as needed, perhaps cross-referencing them with other parts of the CAIF stack or the underlying serial driver architecture if I need to fully understand something. I'll focus on getting a high-level view first and then I'll figure out what I don't know and want to investigate.
|
| 25/2 |
2026/05/23 09:45 |
tool |
codesearch-file-index |
0m
Args: map[SourceFile:drivers/net/caif/caif_serial.c]
Results: map[Entities:[map[Kind:function Name:__check_ser_loop] map[Kind:function Name:__check_ser_use_fcs] map[Kind:function Name:__check_ser_use_stx] map[Kind:function Name:__check_ser_write_chunk] map[Kind:function Name:caif_net_close] map[Kind:function Name:caif_net_open] map[Kind:function Name:caif_ser_exit] map[Kind:function Name:caif_ser_init] map[Kind:function Name:caif_xmit] map[Kind:function Name:caifdev_setup] map[Kind:function Name:debugfs_deinit] map[Kind:function Name:debugfs_init] map[Kind:function Name:debugfs_rx] map[Kind:function Name:handle_tx] map[Kind:function Name:ldisc_close] map[Kind:function Name:ldisc_open] map[Kind:function Name:ldisc_receive] map[Kind:function Name:ldisc_tx_wakeup] map[Kind:function Name:ser_release] map[Kind:function Name:update_tty_status] map[Kind:struct Name:ser_device] map[Kind:global_variable Name:__UNIQUE_ID_addressable_caif_ser_init_1404] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1381] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1382] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1383] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1384] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1385] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1386] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1387] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1388] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1389] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1390] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1391] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1392] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1393] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1394] map[Kind:global_variable Name:__UNIQUE_ID_modinfo_1395] map[Kind:global_variable Name:__exitcall_caif_ser_exit] map[Kind:global_variable Name:__param_ser_loop] map[Kind:global_variable Name:__param_ser_use_fcs] map[Kind:global_variable Name:__param_ser_use_stx] map[Kind:global_variable Name:__param_ser_write_chunk] map[Kind:global_variable Name:__param_str_ser_loop] map[Kind:global_variable Name:__param_str_ser_use_fcs] map[Kind:global_variable Name:__param_str_ser_use_stx] map[Kind:global_variable Name:__param_str_ser_write_chunk] map[Kind:global_variable Name:caif_ldisc] map[Kind:global_variable Name:netdev_ops] map[Kind:global_variable Name:ser_list] map[Kind:global_variable Name:ser_lock] map[Kind:global_variable Name:ser_release_list] map[Kind:global_variable Name:ser_release_work] map[Kind:global_variable Name:ser_use_fcs] map[Kind:global_variable Name:ser_use_stx] map[Kind:global_variable Name:ser_write_chunk]]]
|
| 26/2 |
2026/05/23 09:45 |
llm |
expert |
0m
Model:
Tokens:
input: 30313
output: 46
thoughts: 10
Thoughts: Okay, here's my attempt at summarizing that thought process, keeping in mind I'm speaking to an expert:
**Investigating `ldisc_close`**
Alright, time to get to it. Let's make sure we're on the right track. My immediate thought is to check `ldisc_close`. It's a key function in a system like this, and I need to verify that it's doing what I expect it to do, and that there are no obvious issues lurking in its implementation. Specifically, I need to know: Is it doing what I designed it to? Am I making any incorrect assumptions about its behaviour? I'll probably be thinking about error handling, any resource cleanup that it should be taking care of, and potential race conditions in a multithreaded environment. Let's dig in and make sure it's functioning as it should.
|
| 27/2 |
2026/05/23 09:45 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/caif/caif_serial.c IncludeLines:true Name:ldisc_close]
Results: map[SourceCode: 354: static void ldisc_close(struct tty_struct *tty)
355: {
356: struct ser_device *ser = tty->disc_data;
357:
358: tty_kref_put(ser->tty);
359:
360: spin_lock(&ser_lock);
361: list_move(&ser->node, &ser_release_list);
362: spin_unlock(&ser_lock);
363: schedule_work(&ser_release_work);
364: }
SourceFile:drivers/net/caif/caif_serial.c]
|
| 28/2 |
2026/05/23 09:45 |
llm |
expert |
0m
Model:
Tokens:
input: 30751
output: 45
thoughts: 26
Thoughts: Here's my take on the thought process, summarized as you requested:
**Deconstructing a Potential Serial Port Issue**
Okay, so `ldisc_close` is calling `ser_release_work`. Right, that's the setup. Let's make sure I'm following the correct execution path. I need to get into `ser_release`. I need to fully understand what is supposed to happen here. Iβm thinking there might be something happening related to serial port management or cleanup. Let's dig into that `ser_release` function directly. It's the lynchpin here, so to speak. Understanding what `ser_release` *does* is going to be key to debugging this potential serial port behavior issue.
|
| 29/2 |
2026/05/23 09:45 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/caif/caif_serial.c IncludeLines:true Name:ser_release]
Results: map[SourceCode: 283: static void ser_release(struct work_struct *work)
284: {
285: struct list_head list;
286: struct ser_device *ser, *tmp;
287:
288: spin_lock(&ser_lock);
289: list_replace_init(&ser_release_list, &list);
290: spin_unlock(&ser_lock);
291:
292: if (!list_empty(&list)) {
293: rtnl_lock();
294: list_for_each_entry_safe(ser, tmp, &list, node) {
295: dev_close(ser->dev);
296: unregister_netdevice(ser->dev);
297: debugfs_deinit(ser);
298: }
299: rtnl_unlock();
300: }
301: }
SourceFile:drivers/net/caif/caif_serial.c]
|
| 30/2 |
2026/05/23 09:45 |
llm |
expert |
0m
Model:
Tokens:
input: 31276
output: 45
thoughts: 639
Thoughts: **The Concurrency Conundrum: A Deep Dive into UART and Network Device Interaction**
Okay, so I'm thinking about this `ldisc_close` function, right? That gets called when the line discipline shuts down. But `handle_tx` is triggered via `caif_xmit`, which in turn calls `ndo_start_xmit`. Now, `aoe` is sending packets, using `dev_queue_xmit` and, again, calling `ndo_start_xmit`. The key problem is `dev_close`, because it clears `IFF_UP`, and `aoe` might still be sending packets concurrently. The thing is, `dev_close` is asynchronous, called from `ser_release_work`. This opens a window! The TTY could be in the process of closing, but the network device is *still* up.
If the network device is up, `aoe` can call `dev_queue_xmit` and `handle_tx` gets invoked. That then calls `tty->ops->write`. I'm a bit worried because if the TTY is closed, then what happens? It's possible for `tty->ops->write` to return 0 or an error. Time to double-check `uart_write`.
Okay, here it is: `uart_write`. It takes the `tty`, the buffer, and the count. If `WARN_ON(!state)` is true, it returns `-EL3HLT`. However, look at this! If the port has been closed, `state->port.xmit_buf` will be NULL, then it will return 0.
So it checks `state->port.xmit_buf`. If it's NULL, the function returns 0. That's a problem! If `xmit_buf` is NULL, then `uart_write` will return 0 and the `ndo_start_xmit` will keep looping. This will keep running forever!
Let's dig into this further. We need to check when `xmit_buf` is set to NULL. Is it `uart_port_shutdown` or some other place where it's being freed? Time to go hunting! This concurrency issue is more insidious than I initially thought.
|
| 31/2 |
2026/05/23 09:46 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/serial/serial_core.c IncludeLines:true Name:uart_port_shutdown]
Results: map[SourceCode:1842: /* uport == NULL if uart_port has already been removed */
1843: static void uart_port_shutdown(struct tty_port *port)
1844: {
1845: struct uart_state *state = container_of(port, struct uart_state, port);
1846: struct uart_port *uport = uart_port_check(state);
1847:
1848: /*
1849: * clear delta_msr_wait queue to avoid mem leaks: we may free
1850: * the irq here so the queue might never be woken up. Note
1851: * that we won't end up waiting on delta_msr_wait again since
1852: * any outstanding file descriptors should be pointing at
1853: * hung_up_tty_fops now.
1854: */
1855: wake_up_interruptible(&port->delta_msr_wait);
1856:
1857: if (uport) {
1858: /* Free the IRQ and disable the port. */
1859: uport->ops->shutdown(uport);
1860:
1861: /* Ensure that the IRQ handler isn't running on another CPU. */
1862: synchronize_irq(uport->irq);
1863: }
1864: }
SourceFile:drivers/tty/serial/serial_core.c]
|
| 32/2 |
2026/05/23 09:46 |
llm |
expert |
0m
Model:
Tokens:
input: 32853
output: 18
thoughts: 33
Thoughts: Here's my thought process, as if I were reviewing this code:
**Uncovering a Potential Memory Leak in Serial Transmission**
Alright, hang on a second... I see the `xmit_buf` being used here, but I'm not spotting any immediate `free()` call associated with it. That's a red flag. Could be a classic memory leak in the making. Let's see... a quick mental review of the surrounding code confirms my suspicion: nothing obvious jumps out.
Okay, time to dig deeper. I need to understand the lifecycle of this `xmit_buf`. I'm going to jump into `serial_core.c`. I need to track down every instance of `xmit_buf` within this file. The goal is to see where it's allocated, where it's used, and crucially, where it's deallocated. I'll need to check all related functions. I bet this is just a quick oversight.
|
| 33/2 |
2026/05/23 09:46 |
tool |
grepper |
0m
Args:
Results: map[Output:
Full output is too long, showing 500 out of 771 lines.
Use more precise expression if possible.
[drivers/crypto/omap-sham.c=213=struct omap_sham_dev {
--
drivers/crypto/omap-sham.c-222- u8 polling_mode;
drivers/crypto/omap-sham.c:223: u8 xmit_buf[BUFLEN] OMAP_ALIGNED;
drivers/crypto/omap-sham.c-224-
--
drivers/crypto/omap-sham.c=626=static int omap_sham_copy_sg_lists(struct omap_sham_reqctx *ctx,
--
drivers/crypto/omap-sham.c-648- if (ctx->bufcnt) {
drivers/crypto/omap-sham.c:649: sg_set_buf(tmp, ctx->dd->xmit_buf, ctx->bufcnt);
drivers/crypto/omap-sham.c-650- tmp = sg_next(tmp);
--
drivers/crypto/omap-sham.c=692=static int omap_sham_copy_sgs(struct omap_sham_reqctx *ctx,
--
drivers/crypto/omap-sham.c-707- if (ctx->bufcnt)
drivers/crypto/omap-sham.c:708: memcpy(buf, ctx->dd->xmit_buf, ctx->bufcnt);
drivers/crypto/omap-sham.c-709-
--
drivers/crypto/omap-sham.c=724=static int omap_sham_align_sgs(struct scatterlist *sg,
--
drivers/crypto/omap-sham.c-739- sg_init_table(rctx->sgl, 1);
drivers/crypto/omap-sham.c:740: sg_set_buf(rctx->sgl, rctx->dd->xmit_buf, bufcnt);
drivers/crypto/omap-sham.c-741- rctx->sg = rctx->sgl;
--
drivers/crypto/omap-sham.c-831- sg_init_table(rctx->sgl, 2);
drivers/crypto/omap-sham.c:832: sg_set_buf(rctx->sgl, rctx->dd->xmit_buf, rctx->bufcnt);
drivers/crypto/omap-sham.c-833- sg_chain(rctx->sgl, 2, sg);
--
drivers/crypto/omap-sham.c=842=static int omap_sham_prepare_request(struct crypto_engine *engine, void *areq)
--
drivers/crypto/omap-sham.c-882- if (rctx->bufcnt)
drivers/crypto/omap-sham.c:883: memcpy(rctx->dd->xmit_buf, rctx->buffer, rctx->bufcnt);
drivers/crypto/omap-sham.c-884-
--
drivers/crypto/s5p-sss.c=247=struct s5p_aes_ctx {
--
drivers/crypto/s5p-sss.c-287- * @hash_tasklet: New HASH request scheduling job.
drivers/crypto/s5p-sss.c:288: * @xmit_buf: Buffer for current HASH request transfer into SSS block.
drivers/crypto/s5p-sss.c-289- * @hash_req: Current request sending to SSS HASH block.
--
drivers/crypto/s5p-sss.c=295=struct s5p_aes_dev {
--
drivers/crypto/s5p-sss.c-323-
drivers/crypto/s5p-sss.c:324: u8 xmit_buf[BUFLEN];
drivers/crypto/s5p-sss.c-325- struct ahash_request *hash_req;
--
drivers/crypto/s5p-sss.c=963=static int s5p_hash_xmit_dma(struct s5p_aes_dev *dd, size_t length,
--
drivers/crypto/s5p-sss.c-997- *
drivers/crypto/s5p-sss.c:998: * Allocate new buffer, copy data for HASH into it. If there was xmit_buf
drivers/crypto/s5p-sss.c-999- * filled, copy it first, then copy data from sg into it. Prepare one sgl[0]
--
drivers/crypto/s5p-sss.c=1004=static int s5p_hash_copy_sgs(struct s5p_hash_reqctx *ctx,
--
drivers/crypto/s5p-sss.c-1020- if (ctx->bufcnt)
drivers/crypto/s5p-sss.c:1021: memcpy(buf, ctx->dd->xmit_buf, ctx->bufcnt);
drivers/crypto/s5p-sss.c-1022-
--
drivers/crypto/s5p-sss.c-1041- * Allocate new scatterlist table, copy data for HASH into it. If there was
drivers/crypto/s5p-sss.c:1042: * xmit_buf filled, prepare it first, then copy page, length and offset from
drivers/crypto/s5p-sss.c-1043- * source sg into it, adjusting begin and/or end for skip offset and
--
drivers/crypto/s5p-sss.c=1049=static int s5p_hash_copy_sg_lists(struct s5p_hash_reqctx *ctx,
--
drivers/crypto/s5p-sss.c-1071- if (ctx->bufcnt) {
drivers/crypto/s5p-sss.c:1072: sg_set_buf(tmp, ctx->dd->xmit_buf, ctx->bufcnt);
drivers/crypto/s5p-sss.c-1073- tmp = sg_next(tmp);
--
drivers/crypto/s5p-sss.c=1119=static int s5p_hash_prepare_sgs(struct s5p_hash_reqctx *ctx,
--
drivers/crypto/s5p-sss.c-1170- sg_init_table(ctx->sgl, 2);
drivers/crypto/s5p-sss.c:1171: sg_set_buf(ctx->sgl, ctx->dd->xmit_buf, ctx->bufcnt);
drivers/crypto/s5p-sss.c-1172- sg_chain(ctx->sgl, 2, sg);
--
drivers/crypto/s5p-sss.c=1193=static int s5p_hash_prepare_request(struct ahash_request *req, bool update)
--
drivers/crypto/s5p-sss.c-1224- if (ctx->bufcnt)
drivers/crypto/s5p-sss.c:1225: memcpy(ctx->dd->xmit_buf, ctx->buffer, ctx->bufcnt);
drivers/crypto/s5p-sss.c-1226-
--
drivers/crypto/s5p-sss.c-1237- /* copy hash_later bytes from end of req->src */
drivers/crypto/s5p-sss.c:1238: /* previous bytes are in xmit_buf, so no overwrite */
drivers/crypto/s5p-sss.c-1239- memcpy_from_sglist(ctx->buffer, req->src,
--
drivers/crypto/s5p-sss.c-1251- /* first update didn't fill up buffer */
drivers/crypto/s5p-sss.c:1252: memcpy_from_sglist(ctx->dd->xmit_buf, req->src,
drivers/crypto/s5p-sss.c-1253- 0, xmit_len);
--
drivers/crypto/s5p-sss.c-1256- sg_init_table(ctx->sgl, 1);
drivers/crypto/s5p-sss.c:1257: sg_set_buf(ctx->sgl, ctx->dd->xmit_buf, xmit_len);
drivers/crypto/s5p-sss.c-1258-
--
drivers/crypto/stm32/stm32-hash.c=193=struct stm32_hash_dev {
--
drivers/crypto/stm32/stm32-hash.c-199- phys_addr_t phys_base;
drivers/crypto/stm32/stm32-hash.c:200: u8 xmit_buf[HASH_BUFLEN] __aligned(sizeof(u32));
drivers/crypto/stm32/stm32-hash.c-201- u32 dma_mode;
--
drivers/crypto/stm32/stm32-hash.c=1102=static int stm32_hash_copy_sgs(struct stm32_hash_request_ctx *rctx,
--
drivers/crypto/stm32/stm32-hash.c-1118- if (state->bufcnt)
drivers/crypto/stm32/stm32-hash.c:1119: memcpy(buf, rctx->hdev->xmit_buf, state->bufcnt);
drivers/crypto/stm32/stm32-hash.c-1120-
--
drivers/crypto/stm32/stm32-hash.c=1135=static int stm32_hash_align_sgs(struct scatterlist *sg,
--
drivers/crypto/stm32/stm32-hash.c-1152- sg_init_table(rctx->sgl, 1);
drivers/crypto/stm32/stm32-hash.c:1153: sg_set_buf(rctx->sgl, rctx->hdev->xmit_buf, bufcnt);
drivers/crypto/stm32/stm32-hash.c-1154- rctx->sg = rctx->sgl;
--
drivers/crypto/stm32/stm32-hash.c-1242- sg_init_table(rctx->sgl, 2);
drivers/crypto/stm32/stm32-hash.c:1243: sg_set_buf(rctx->sgl, rctx->hdev->xmit_buf, state->bufcnt);
drivers/crypto/stm32/stm32-hash.c-1244- sg_chain(rctx->sgl, 2, sg);
--
drivers/crypto/stm32/stm32-hash.c=1253=static int stm32_hash_prepare_request(struct ahash_request *req)
--
drivers/crypto/stm32/stm32-hash.c-1303- if (state->bufcnt)
drivers/crypto/stm32/stm32-hash.c:1304: memcpy(hdev->xmit_buf, state->buffer, state->bufcnt);
drivers/crypto/stm32/stm32-hash.c-1305-
--
drivers/ipack/devices/ipoctal.c=201=static void ipoctal_irq_tx(struct ipoctal_channel *channel)
--
drivers/ipack/devices/ipoctal.c-209- spin_lock(&channel->lock);
drivers/ipack/devices/ipoctal.c:210: value = channel->tty_port.xmit_buf[*pointer_write];
drivers/ipack/devices/ipoctal.c-211- iowrite8(value, &channel->regs->w.thr);
--
drivers/ipack/devices/ipoctal.c=272=static int ipoctal_inst_slot(struct ipoctal *ipoctal, unsigned int bus_nr,
--
drivers/ipack/devices/ipoctal.c-397- tty_port_init(&channel->tty_port);
drivers/ipack/devices/ipoctal.c:398: res = tty_port_alloc_xmit_buf(&channel->tty_port);
drivers/ipack/devices/ipoctal.c-399- if (res)
--
drivers/ipack/devices/ipoctal.c-411- dev_err(&ipoctal->dev->dev, "Failed to register tty device.\n");
drivers/ipack/devices/ipoctal.c:412: tty_port_free_xmit_buf(&channel->tty_port);
drivers/ipack/devices/ipoctal.c-413- tty_port_destroy(&channel->tty_port);
--
drivers/ipack/devices/ipoctal.c=437=static inline size_t ipoctal_copy_write_buffer(struct ipoctal_channel *channel,
--
drivers/ipack/devices/ipoctal.c-447- spin_lock_irqsave(&channel->lock, flags);
drivers/ipack/devices/ipoctal.c:448: channel->tty_port.xmit_buf[*pointer_read] = buf[i];
drivers/ipack/devices/ipoctal.c-449- *pointer_read = (*pointer_read + 1) % PAGE_SIZE;
--
drivers/ipack/devices/ipoctal.c=708=static void __ipoctal_remove(struct ipoctal *ipoctal)
--
drivers/ipack/devices/ipoctal.c-720- tty_unregister_device(ipoctal->tty_drv, i);
drivers/ipack/devices/ipoctal.c:721: tty_port_free_xmit_buf(&channel->tty_port);
drivers/ipack/devices/ipoctal.c-722- tty_port_destroy(&channel->tty_port);
--
drivers/net/ethernet/i825xx/sun3_82586.c=145=struct priv
--
drivers/net/ethernet/i825xx/sun3_82586.c-154- volatile struct scb_struct *scb; /* volatile is important */
drivers/net/ethernet/i825xx/sun3_82586.c:155: volatile struct tbd_struct *xmit_buffs[NUM_XMIT_BUFFS];
drivers/net/ethernet/i825xx/sun3_82586.c-156- volatile struct transmit_cmd_struct *xmit_cmds[NUM_XMIT_BUFFS];
--
drivers/net/ethernet/i825xx/sun3_82586.c=401=static int init586(struct net_device *dev)
--
drivers/net/ethernet/i825xx/sun3_82586.c-581- ptr = (char *) ptr + XMIT_BUFF_SIZE;
drivers/net/ethernet/i825xx/sun3_82586.c:582: p->xmit_buffs[i] = (struct tbd_struct *)ptr; /* TBD */
drivers/net/ethernet/i825xx/sun3_82586.c-583- ptr = (char *) ptr + sizeof(struct tbd_struct);
--
drivers/net/ethernet/i825xx/sun3_82586.c-589- memset((char *)(p->xmit_cmds[i]) ,0, sizeof(struct transmit_cmd_struct));
drivers/net/ethernet/i825xx/sun3_82586.c:590: memset((char *)(p->xmit_buffs[i]),0, sizeof(struct tbd_struct));
drivers/net/ethernet/i825xx/sun3_82586.c-591- p->xmit_cmds[i]->cmd_link = make16(p->nop_cmds[(i+1)%NUM_XMIT_BUFFS]);
--
drivers/net/ethernet/i825xx/sun3_82586.c-593- p->xmit_cmds[i]->cmd_cmd = swab16(CMD_XMIT | CMD_INT);
drivers/net/ethernet/i825xx/sun3_82586.c:594: p->xmit_cmds[i]->tbd_offset = make16((p->xmit_buffs[i]));
drivers/net/ethernet/i825xx/sun3_82586.c:595: p->xmit_buffs[i]->next = 0xffff;
drivers/net/ethernet/i825xx/sun3_82586.c:596: p->xmit_buffs[i]->buffer = make24((p->xmit_cbuffs[i]));
drivers/net/ethernet/i825xx/sun3_82586.c-597- }
--
drivers/net/ethernet/i825xx/sun3_82586.c=1004=sun3_82586_send_packet(struct sk_buff *skb, struct net_device *dev)
--
drivers/net/ethernet/i825xx/sun3_82586.c-1047-
drivers/net/ethernet/i825xx/sun3_82586.c:1048: p->xmit_buffs[0]->size = swab16(TBD_LAST | len);
drivers/net/ethernet/i825xx/sun3_82586.c-1049- for(i=0;i<16;i++)
--
drivers/net/ethernet/i825xx/sun3_82586.c-1073- next_nop = (p->nop_point + 1) & 0x1;
drivers/net/ethernet/i825xx/sun3_82586.c:1074: p->xmit_buffs[0]->size = swab16(TBD_LAST | len);
drivers/net/ethernet/i825xx/sun3_82586.c-1075-
--
drivers/net/ethernet/i825xx/sun3_82586.c-1084-#else
drivers/net/ethernet/i825xx/sun3_82586.c:1085: p->xmit_buffs[p->xmit_count]->size = swab16(TBD_LAST | len);
drivers/net/ethernet/i825xx/sun3_82586.c-1086- if( (next_nop = p->xmit_count + 1) == NUM_XMIT_BUFFS )
--
drivers/net/wireless/mediatek/mt76/mt76.h=685=struct mt76_sdio {
--
drivers/net/wireless/mediatek/mt76/mt76.h-690-
drivers/net/wireless/mediatek/mt76/mt76.h:691: u8 *xmit_buf;
drivers/net/wireless/mediatek/mt76/mt76.h:692: u32 xmit_buf_sz;
drivers/net/wireless/mediatek/mt76/mt76.h-693-
--
drivers/net/wireless/mediatek/mt76/sdio.c=635=int mt76s_init(struct mt76_dev *dev, struct sdio_func *func,
--
drivers/net/wireless/mediatek/mt76/sdio.c-667- func->card->host->max_blk_count);
drivers/net/wireless/mediatek/mt76/sdio.c:668: dev->sdio.xmit_buf_sz = min_t(u32, host_max_cap, MT76S_XMIT_BUF_SZ);
drivers/net/wireless/mediatek/mt76/sdio.c:669: dev->sdio.xmit_buf = devm_kmalloc(dev->dev, dev->sdio.xmit_buf_sz,
drivers/net/wireless/mediatek/mt76/sdio.c-670- GFP_KERNEL);
drivers/net/wireless/mediatek/mt76/sdio.c:671: if (!dev->sdio.xmit_buf)
drivers/net/wireless/mediatek/mt76/sdio.c-672- err = -ENOMEM;
--
drivers/net/wireless/mediatek/mt76/sdio_txrx.c=245=static int mt76s_tx_run_queue(struct mt76_dev *dev, struct mt76_queue *q)
--
drivers/net/wireless/mediatek/mt76/sdio_txrx.c-275- pad = roundup(e->skb->len, 4) - e->skb->len;
drivers/net/wireless/mediatek/mt76/sdio_txrx.c:276: if (len + e->skb->len + pad + 4 > dev->sdio.xmit_buf_sz)
drivers/net/wireless/mediatek/mt76/sdio_txrx.c-277- break;
--
drivers/net/wireless/mediatek/mt76/sdio_txrx.c-282-
drivers/net/wireless/mediatek/mt76/sdio_txrx.c:283: memcpy(sdio->xmit_buf + len, e->skb->data, skb_headlen(e->skb));
drivers/net/wireless/mediatek/mt76/sdio_txrx.c-284- len += skb_headlen(e->skb);
--
drivers/net/wireless/mediatek/mt76/sdio_txrx.c-287- skb_walk_frags(e->skb, iter) {
drivers/net/wireless/mediatek/mt76/sdio_txrx.c:288: memcpy(sdio->xmit_buf + len, iter->data, iter->len);
drivers/net/wireless/mediatek/mt76/sdio_txrx.c-289- len += iter->len;
--
drivers/net/wireless/mediatek/mt76/sdio_txrx.c-293- if (unlikely(pad)) {
drivers/net/wireless/mediatek/mt76/sdio_txrx.c:294: memset(sdio->xmit_buf + len, 0, pad);
drivers/net/wireless/mediatek/mt76/sdio_txrx.c-295- len += pad;
--
drivers/net/wireless/mediatek/mt76/sdio_txrx.c-302- if (nframes) {
drivers/net/wireless/mediatek/mt76/sdio_txrx.c:303: memset(sdio->xmit_buf + len, 0, 4);
drivers/net/wireless/mediatek/mt76/sdio_txrx.c:304: err = __mt76s_xmit_queue(dev, sdio->xmit_buf, len + 4);
drivers/net/wireless/mediatek/mt76/sdio_txrx.c-305- if (err)
--
drivers/staging/rtl8723bs/core/rtw_mlme_ext.c=1909=static struct xmit_frame *_alloc_mgtxmitframe(struct xmit_priv *pxmitpriv, bool once)
--
drivers/staging/rtl8723bs/core/rtw_mlme_ext.c-1911- struct xmit_frame *pmgntframe;
drivers/staging/rtl8723bs/core/rtw_mlme_ext.c:1912: struct xmit_buf *pxmitbuf;
drivers/staging/rtl8723bs/core/rtw_mlme_ext.c-1913-
--
drivers/staging/rtl8723bs/core/rtw_mlme_ext.c=2015=s32 dump_mgntframe_and_wait(struct adapter *padapter, struct xmit_frame *pmgntframe, int timeout_ms)
--
drivers/staging/rtl8723bs/core/rtw_mlme_ext.c-2019- struct xmit_priv *pxmitpriv = &padapter->xmitpriv;
drivers/staging/rtl8723bs/core/rtw_mlme_ext.c:2020: struct xmit_buf *pxmitbuf = pmgntframe->pxmitbuf;
drivers/staging/rtl8723bs/core/rtw_mlme_ext.c-2021- struct submit_ctx sctx;
--
drivers/staging/rtl8723bs/core/rtw_xmit.c=34=s32 _rtw_init_xmit_priv(struct xmit_priv *pxmitpriv, struct adapter *padapter)
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-36- int i;
drivers/staging/rtl8723bs/core/rtw_xmit.c:37: struct xmit_buf *pxmitbuf;
drivers/staging/rtl8723bs/core/rtw_xmit.c-38- struct xmit_frame *pxframe;
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-103-
drivers/staging/rtl8723bs/core/rtw_xmit.c:104: /* init xmit_buf */
drivers/staging/rtl8723bs/core/rtw_xmit.c-105- INIT_LIST_HEAD(&pxmitpriv->free_xmitbuf_queue.queue);
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-109-
drivers/staging/rtl8723bs/core/rtw_xmit.c:110: pxmitpriv->pallocated_xmitbuf = vzalloc(NR_XMITBUFF * sizeof(struct xmit_buf) + 4);
drivers/staging/rtl8723bs/core/rtw_xmit.c-111-
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-118-
drivers/staging/rtl8723bs/core/rtw_xmit.c:119: pxmitbuf = (struct xmit_buf *)pxmitpriv->pxmitbuf;
drivers/staging/rtl8723bs/core/rtw_xmit.c-120-
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-192-
drivers/staging/rtl8723bs/core/rtw_xmit.c:193: pxmitpriv->pallocated_xmit_extbuf = vzalloc(NR_XMIT_EXTBUFF * sizeof(struct xmit_buf) + 4);
drivers/staging/rtl8723bs/core/rtw_xmit.c-194-
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-201-
drivers/staging/rtl8723bs/core/rtw_xmit.c:202: pxmitbuf = (struct xmit_buf *)pxmitpriv->pxmit_extbuf;
drivers/staging/rtl8723bs/core/rtw_xmit.c-203-
--
drivers/staging/rtl8723bs/core/rtw_xmit.c=273=void _rtw_free_xmit_priv(struct xmit_priv *pxmitpriv)
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-277- struct xmit_frame *pxmitframe = (struct xmit_frame *) pxmitpriv->pxmit_frame_buf;
drivers/staging/rtl8723bs/core/rtw_xmit.c:278: struct xmit_buf *pxmitbuf = (struct xmit_buf *)pxmitpriv->pxmitbuf;
drivers/staging/rtl8723bs/core/rtw_xmit.c-279-
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-311- /* free xmit extension buff */
drivers/staging/rtl8723bs/core/rtw_xmit.c:312: pxmitbuf = (struct xmit_buf *)pxmitpriv->pxmit_extbuf;
drivers/staging/rtl8723bs/core/rtw_xmit.c-313- for (i = 0; i < NR_XMIT_EXTBUFF; i++) {
--
drivers/staging/rtl8723bs/core/rtw_xmit.c=1370=void rtw_count_tx_stats(struct adapter *padapter, struct xmit_frame *pxmitframe, int sz)
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-1397-
drivers/staging/rtl8723bs/core/rtw_xmit.c:1398:static struct xmit_buf *__rtw_alloc_cmd_xmitbuf(struct xmit_priv *pxmitpriv,
drivers/staging/rtl8723bs/core/rtw_xmit.c-1399- enum cmdbuf_type buf_type)
drivers/staging/rtl8723bs/core/rtw_xmit.c-1400-{
drivers/staging/rtl8723bs/core/rtw_xmit.c:1401: struct xmit_buf *pxmitbuf = NULL;
drivers/staging/rtl8723bs/core/rtw_xmit.c-1402-
--
drivers/staging/rtl8723bs/core/rtw_xmit.c=1419=struct xmit_frame *__rtw_alloc_cmdxmitframe(struct xmit_priv *pxmitpriv,
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-1422- struct xmit_frame *pcmdframe;
drivers/staging/rtl8723bs/core/rtw_xmit.c:1423: struct xmit_buf *pxmitbuf;
drivers/staging/rtl8723bs/core/rtw_xmit.c-1424-
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-1445-
drivers/staging/rtl8723bs/core/rtw_xmit.c:1446:struct xmit_buf *rtw_alloc_xmitbuf_ext(struct xmit_priv *pxmitpriv)
drivers/staging/rtl8723bs/core/rtw_xmit.c-1447-{
drivers/staging/rtl8723bs/core/rtw_xmit.c-1448- unsigned long irqL;
drivers/staging/rtl8723bs/core/rtw_xmit.c:1449: struct xmit_buf *pxmitbuf = NULL;
drivers/staging/rtl8723bs/core/rtw_xmit.c-1450- struct list_head *plist, *phead;
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-1461-
drivers/staging/rtl8723bs/core/rtw_xmit.c:1462: pxmitbuf = container_of(plist, struct xmit_buf, list);
drivers/staging/rtl8723bs/core/rtw_xmit.c-1463-
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-1485-
drivers/staging/rtl8723bs/core/rtw_xmit.c:1486:s32 rtw_free_xmitbuf_ext(struct xmit_priv *pxmitpriv, struct xmit_buf *pxmitbuf)
drivers/staging/rtl8723bs/core/rtw_xmit.c-1487-{
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-1505-
drivers/staging/rtl8723bs/core/rtw_xmit.c:1506:struct xmit_buf *rtw_alloc_xmitbuf(struct xmit_priv *pxmitpriv)
drivers/staging/rtl8723bs/core/rtw_xmit.c-1507-{
drivers/staging/rtl8723bs/core/rtw_xmit.c-1508- unsigned long irqL;
drivers/staging/rtl8723bs/core/rtw_xmit.c:1509: struct xmit_buf *pxmitbuf = NULL;
drivers/staging/rtl8723bs/core/rtw_xmit.c-1510- struct list_head *plist, *phead;
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-1521-
drivers/staging/rtl8723bs/core/rtw_xmit.c:1522: pxmitbuf = container_of(plist, struct xmit_buf, list);
drivers/staging/rtl8723bs/core/rtw_xmit.c-1523-
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-1546-
drivers/staging/rtl8723bs/core/rtw_xmit.c:1547:s32 rtw_free_xmitbuf(struct xmit_priv *pxmitpriv, struct xmit_buf *pxmitbuf)
drivers/staging/rtl8723bs/core/rtw_xmit.c-1548-{
--
drivers/staging/rtl8723bs/core/rtw_xmit.c=2312=void xmit_delivery_enabled_frames(struct adapter *padapter, struct sta_info *psta)
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-2375-
drivers/staging/rtl8723bs/core/rtw_xmit.c:2376:void enqueue_pending_xmitbuf(struct xmit_priv *pxmitpriv, struct xmit_buf *pxmitbuf)
drivers/staging/rtl8723bs/core/rtw_xmit.c-2377-{
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-2390-
drivers/staging/rtl8723bs/core/rtw_xmit.c:2391:void enqueue_pending_xmitbuf_to_head(struct xmit_priv *pxmitpriv, struct xmit_buf *pxmitbuf)
drivers/staging/rtl8723bs/core/rtw_xmit.c-2392-{
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-2402-
drivers/staging/rtl8723bs/core/rtw_xmit.c:2403:struct xmit_buf *dequeue_pending_xmitbuf(struct xmit_priv *pxmitpriv)
drivers/staging/rtl8723bs/core/rtw_xmit.c-2404-{
drivers/staging/rtl8723bs/core/rtw_xmit.c:2405: struct xmit_buf *pxmitbuf;
drivers/staging/rtl8723bs/core/rtw_xmit.c-2406- struct __queue *pqueue;
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-2417- plist = get_next(phead);
drivers/staging/rtl8723bs/core/rtw_xmit.c:2418: pxmitbuf = container_of(plist, struct xmit_buf, list);
drivers/staging/rtl8723bs/core/rtw_xmit.c-2419- list_del_init(&pxmitbuf->list);
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-2426-
drivers/staging/rtl8723bs/core/rtw_xmit.c:2427:struct xmit_buf *dequeue_pending_xmitbuf_under_survey(struct xmit_priv *pxmitpriv)
drivers/staging/rtl8723bs/core/rtw_xmit.c-2428-{
drivers/staging/rtl8723bs/core/rtw_xmit.c:2429: struct xmit_buf *pxmitbuf;
drivers/staging/rtl8723bs/core/rtw_xmit.c-2430- struct __queue *pqueue;
--
drivers/staging/rtl8723bs/core/rtw_xmit.c-2447-
drivers/staging/rtl8723bs/core/rtw_xmit.c:2448: pxmitbuf = container_of(plist, struct xmit_buf, list);
drivers/staging/rtl8723bs/core/rtw_xmit.c-2449-
--
drivers/staging/rtl8723bs/hal/hal_intf.c=279=s32 rtw_hal_xmit_thread_handler(struct adapter *padapter)
drivers/staging/rtl8723bs/hal/hal_intf.c-280-{
drivers/staging/rtl8723bs/hal/hal_intf.c:281: return rtl8723bs_xmit_buf_handler(padapter);
drivers/staging/rtl8723bs/hal/hal_intf.c-282-}
--
drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c=2925=void rtl8723b_stop_thread(struct adapter *padapter)
--
drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c-2928-
drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c:2929: /* stop xmit_buf_thread */
drivers/staging/rtl8723bs/hal/rtl8723b_hal_init.c-2930- if (xmitpriv->SdioXmitThread) {
--
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c=36=static s32 rtl8723_dequeue_writeport(struct adapter *padapter)
--
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-40- struct dvobj_priv *pdvobjpriv = adapter_to_dvobj(padapter);
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c:41: struct xmit_buf *pxmitbuf;
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-42- struct adapter *pri_padapter = padapter;
--
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-120- */
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c:121:s32 rtl8723bs_xmit_buf_handler(struct adapter *padapter)
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-122-{
--
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c=166=static s32 xmit_xmitframes(struct adapter *padapter, struct xmit_priv *pxmitpriv)
--
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-175- struct __queue *pframe_queue;
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c:176: struct xmit_buf *pxmitbuf;
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-177- u32 txlen, max_xmit_len;
--
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-231-
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c:232: /* check xmit_buf size enough or not */
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-233- txlen = txdesc_size + rtw_wlan_pkt_size(pxmitframe);
--
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-259- netdev_err(padapter->pnetdev,
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c:260: "%s: xmit_buf is not enough!\n",
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-261- __func__);
--
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-322-
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c:323: /* dump xmit_buf to hw tx fifo */
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-324- if (pxmitbuf) {
--
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c=423=s32 rtl8723bs_mgnt_xmit(
--
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-428- struct pkt_attrib *pattrib = &pmgntframe->attrib;
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c:429: struct xmit_buf *pxmitbuf = pmgntframe->pxmitbuf;
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-430- struct xmit_priv *pxmitpriv = &padapter->xmitpriv;
--
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c=545=void rtl8723bs_free_xmit_priv(struct adapter *padapter)
--
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-547- struct xmit_priv *pxmitpriv = &padapter->xmitpriv;
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c:548: struct xmit_buf *pxmitbuf;
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-549- struct __queue *pqueue = &pxmitpriv->pending_xmitbuf_queue;
--
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-570-
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c:571: pxmitbuf = container_of(plist, struct xmit_buf, list);
drivers/staging/rtl8723bs/hal/rtl8723bs_xmit.c-572- rtw_free_xmitframe(pxmitpriv, (struct xmit_frame *)pxmitbuf->priv_data);
--
drivers/staging/rtl8723bs/hal/sdio_ops.c=428=static u32 sdio_write_port(
--
drivers/staging/rtl8723bs/hal/sdio_ops.c-437- s32 err;
drivers/staging/rtl8723bs/hal/sdio_ops.c:438: struct xmit_buf *xmitbuf = (struct xmit_buf *)mem;
drivers/staging/rtl8723bs/hal/sdio_ops.c-439-
--
drivers/staging/rtl8723bs/include/rtl8723b_xmit.h=414=s32 rtl8723bs_hal_xmitframe_enqueue(struct adapter *padapter, struct xmit_frame *pxmitframe);
drivers/staging/rtl8723bs/include/rtl8723b_xmit.h:415:s32 rtl8723bs_xmit_buf_handler(struct adapter *padapter);
drivers/staging/rtl8723bs/include/rtl8723b_xmit.h-416-int rtl8723bs_xmit_thread(void *context);
--
drivers/staging/rtl8723bs/include/rtw_xmit.h=229=void rtw_sctx_done(struct submit_ctx **sctx);
drivers/staging/rtl8723bs/include/rtw_xmit.h-230-
drivers/staging/rtl8723bs/include/rtw_xmit.h:231:struct xmit_buf {
drivers/staging/rtl8723bs/include/rtw_xmit.h-232- struct list_head list;
--
drivers/staging/rtl8723bs/include/rtw_xmit.h=265=struct xmit_frame {
--
drivers/staging/rtl8723bs/include/rtw_xmit.h-277-
drivers/staging/rtl8723bs/include/rtw_xmit.h:278: struct xmit_buf *pxmitbuf;
drivers/staging/rtl8723bs/include/rtw_xmit.h-279-
--
drivers/staging/rtl8723bs/include/rtw_xmit.h=338=struct xmit_priv {
--
drivers/staging/rtl8723bs/include/rtw_xmit.h-407-
drivers/staging/rtl8723bs/include/rtw_xmit.h:408: struct xmit_buf pcmd_xmitbuf[CMDBUF_MAX];
drivers/staging/rtl8723bs/include/rtw_xmit.h-409-
--
drivers/staging/rtl8723bs/include/rtw_xmit.h=419=extern struct xmit_frame *__rtw_alloc_cmdxmitframe(struct xmit_priv *pxmitpriv,
--
drivers/staging/rtl8723bs/include/rtw_xmit.h-423-
drivers/staging/rtl8723bs/include/rtw_xmit.h:424:extern struct xmit_buf *rtw_alloc_xmitbuf_ext(struct xmit_priv *pxmitpriv);
drivers/staging/rtl8723bs/include/rtw_xmit.h:425:extern s32 rtw_free_xmitbuf_ext(struct xmit_priv *pxmitpriv, struct xmit_buf *pxmitbuf);
drivers/staging/rtl8723bs/include/rtw_xmit.h-426-
drivers/staging/rtl8723bs/include/rtw_xmit.h:427:extern struct xmit_buf *rtw_alloc_xmitbuf(struct xmit_priv *pxmitpriv);
drivers/staging/rtl8723bs/include/rtw_xmit.h:428:extern s32 rtw_free_xmitbuf(struct xmit_priv *pxmitpriv, struct xmit_buf *pxmitbuf);
drivers/staging/rtl8723bs/include/rtw_xmit.h-429-
--
drivers/staging/rtl8723bs/include/rtw_xmit.h=474=u8 qos_acm(u8 acm_mask, u8 priority);
drivers/staging/rtl8723bs/include/rtw_xmit.h-475-
drivers/staging/rtl8723bs/include/rtw_xmit.h:476:void enqueue_pending_xmitbuf(struct xmit_priv *pxmitpriv, struct xmit_buf *pxmitbuf);
drivers/staging/rtl8723bs/include/rtw_xmit.h:477:void enqueue_pending_xmitbuf_to_head(struct xmit_priv *pxmitpriv, struct xmit_buf *pxmitbuf);
drivers/staging/rtl8723bs/include/rtw_xmit.h:478:struct xmit_buf *dequeue_pending_xmitbuf(struct xmit_priv *pxmitpriv);
drivers/staging/rtl8723bs/include/rtw_xmit.h:479:struct xmit_buf *dequeue_pending_xmitbuf_under_survey(struct xmit_priv *pxmitpriv);
drivers/staging/rtl8723bs/include/rtw_xmit.h-480-signed int check_pending_xmitbuf(struct xmit_priv *pxmitpriv);
--
drivers/staging/rtl8723bs/include/rtw_xmit.h=486=void rtw_ack_tx_done(struct xmit_priv *pxmitpriv, int status);
drivers/staging/rtl8723bs/include/rtw_xmit.h-487-
drivers/staging/rtl8723bs/include/rtw_xmit.h:488:/* include after declaring struct xmit_buf, in order to avoid warning */
drivers/staging/rtl8723bs/include/rtw_xmit.h-489-#include <xmit_osdep.h>
--
drivers/staging/rtl8723bs/include/xmit_osdep.h=25=struct xmit_frame;
drivers/staging/rtl8723bs/include/xmit_osdep.h:26:struct xmit_buf;
drivers/staging/rtl8723bs/include/xmit_osdep.h-27-
--
drivers/staging/rtl8723bs/include/xmit_osdep.h=31=void rtw_os_xmit_schedule(struct adapter *padapter);
drivers/staging/rtl8723bs/include/xmit_osdep.h-32-
drivers/staging/rtl8723bs/include/xmit_osdep.h:33:int rtw_os_xmit_resource_alloc(struct adapter *padapter, struct xmit_buf *pxmitbuf, u32 alloc_sz, u8 flag);
drivers/staging/rtl8723bs/include/xmit_osdep.h:34:void rtw_os_xmit_resource_free(struct adapter *padapter, struct xmit_buf *pxmitbuf, u32 free_sz, u8 flag);
drivers/staging/rtl8723bs/include/xmit_osdep.h-35-
--
drivers/staging/rtl8723bs/os_dep/xmit_linux.c=39=signed int rtw_endofpktfile(struct pkt_file *pfile)
--
drivers/staging/rtl8723bs/os_dep/xmit_linux.c-45-
drivers/staging/rtl8723bs/os_dep/xmit_linux.c:46:int rtw_os_xmit_resource_alloc(struct adapter *padapter, struct xmit_buf *pxmitbuf, u32 alloc_sz, u8 flag)
drivers/staging/rtl8723bs/os_dep/xmit_linux.c-47-{
--
drivers/staging/rtl8723bs/os_dep/xmit_linux.c-58-
drivers/staging/rtl8723bs/os_dep/xmit_linux.c:59:void rtw_os_xmit_resource_free(struct adapter *padapter, struct xmit_buf *pxmitbuf, u32 free_sz, u8 flag)
drivers/staging/rtl8723bs/os_dep/xmit_linux.c-60-{
--
drivers/tty/mips_ejtag_fdc.c=84=struct mips_ejtag_fdc_tty;
--
drivers/tty/mips_ejtag_fdc.c-93- * @rx_buf: Read buffer.
drivers/tty/mips_ejtag_fdc.c:94: * @xmit_lock: Lock for xmit_*, and port.xmit_buf.
drivers/tty/mips_ejtag_fdc.c-95- * This protects between user context and kernel thread.
--
drivers/tty/mips_ejtag_fdc.c=415=static unsigned int mips_ejtag_fdc_put_chan(struct mips_ejtag_fdc_tty *priv,
--
drivers/tty/mips_ejtag_fdc.c-427- if (dport->xmit_cnt) {
drivers/tty/mips_ejtag_fdc.c:428: ptrs[0] = dport->port.xmit_buf + dport->xmit_tail;
drivers/tty/mips_ejtag_fdc.c-429- sizes[0] = min_t(unsigned int,
--
drivers/tty/mips_ejtag_fdc.c-431- dport->xmit_cnt);
drivers/tty/mips_ejtag_fdc.c:432: ptrs[1] = dport->port.xmit_buf;
drivers/tty/mips_ejtag_fdc.c-433- sizes[1] = dport->xmit_cnt - sizes[0];
--
drivers/tty/mips_ejtag_fdc.c=696=static int mips_ejtag_fdc_tty_port_activate(struct tty_port *port,
--
drivers/tty/mips_ejtag_fdc.c-703- /* Allocate the buffer we use for writing data */
drivers/tty/mips_ejtag_fdc.c:704: if (tty_port_alloc_xmit_buf(port) < 0)
drivers/tty/mips_ejtag_fdc.c-705- goto err;
--
drivers/tty/mips_ejtag_fdc.c-717-err_free_xmit:
drivers/tty/mips_ejtag_fdc.c:718: tty_port_free_xmit_buf(port);
drivers/tty/mips_ejtag_fdc.c-719-err:
--
drivers/tty/mips_ejtag_fdc.c=723=static void mips_ejtag_fdc_tty_port_shutdown(struct tty_port *port)
--
drivers/tty/mips_ejtag_fdc.c-751- /* Free the write buffer */
]
]
|
| 34/2 |
2026/05/23 09:46 |
llm |
expert |
0m
Model:
Tokens:
input: 47224
output: 45
thoughts: 38
Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience:
**Analyzing `xmit_buf` and its Context**
Right, so `xmit_buf`... that's a classic. My gut feeling is immediately pointing me towards either the `tty_port` or `uart_port` structure. Those are the usual suspects when you're dealing with serial port drivers. Let's not waste any time guessing, though; time to confirm that hypothesis. A quick dive into `uart_port_startup` should give me the confirmation I need. I'm betting the farm on that function having some useful context around how `xmit_buf` is initialized or used. Let's see what's what.
|
| 35/2 |
2026/05/23 09:46 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/serial/serial_core.c IncludeLines:true Name:uart_port_startup]
Results: map[SourceCode: 299: /*
300: * Startup the port. This will be called once per open. All calls
301: * will be serialised by the per-port mutex.
302: */
303: static int uart_port_startup(struct tty_struct *tty, struct uart_state *state,
304: bool init_hw)
305: {
306: struct uart_port *uport = uart_port_check(state);
307: int retval;
308:
309: if (uport->type == PORT_UNKNOWN)
310: return 1;
311:
312: /*
313: * Make sure the device is in D0 state.
314: */
315: uart_change_pm(state, UART_PM_STATE_ON);
316:
317: retval = uart_alloc_xmit_buf(&state->port);
318: if (retval)
319: return retval;
320:
321: retval = uport->ops->startup(uport);
322: if (retval == 0) {
323: if (uart_console(uport) && uport->cons->cflag) {
324: tty->termios.c_cflag = uport->cons->cflag;
325: tty->termios.c_ispeed = uport->cons->ispeed;
326: tty->termios.c_ospeed = uport->cons->ospeed;
327: uport->cons->cflag = 0;
328: uport->cons->ispeed = 0;
329: uport->cons->ospeed = 0;
330: }
331: /*
332: * Initialise the hardware port settings.
333: */
334: uart_change_line_settings(tty, state, NULL);
335:
336: /*
337: * Setup the RTS and DTR signals once the
338: * port is open and ready to respond.
339: */
340: if (init_hw && C_BAUD(tty))
341: uart_port_dtr_rts(uport, true);
342: }
343:
344: /*
345: * This is to allow setserial on this port. People may want to set
346: * port/irq/type and then reconfigure the port properly if it failed
347: * now.
348: */
349: if (retval && capable(CAP_SYS_ADMIN))
350: return 1;
351:
352: return retval;
353: }
SourceFile:drivers/tty/serial/serial_core.c]
|
| 36/2 |
2026/05/23 09:46 |
llm |
expert |
0m
Model:
Tokens:
input: 48288
output: 48
thoughts: 30
Thoughts: Here's my thought process, as if I were analyzing that code:
**Diving into the UART Transmit Buffer Allocation**
Okay, first things first, I see `uart_alloc_xmit_buf` being called. That's a key function in any UART transmit setup; it's where the rubber meets the road, as they say, for data actually going *out* the serial port. So, let's drill down into that function and understand precisely what's happening. I need to see how the system is managing and allocating the transmit buffer space. What kind of buffering scheme is used? Is it a ring buffer? A linked list? How is it managing pointers and ensuring thread safety? Are there any potential race conditions that jump out? This is where the details are; I need to understand this allocation scheme *thoroughly* to ensure optimal performance and robustness. Let's see how this thing actually works.
|
| 37/2 |
2026/05/23 09:46 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/serial/serial_core.c IncludeLines:true Name:uart_alloc_xmit_buf]
Results: map[SourceCode: 244: static int uart_alloc_xmit_buf(struct tty_port *port)
245: {
246: struct uart_state *state = container_of(port, struct uart_state, port);
247: struct uart_port *uport;
248: unsigned long flags;
249: unsigned long page;
250:
251: /*
252: * Initialise and allocate the transmit and temporary
253: * buffer.
254: */
255: page = get_zeroed_page(GFP_KERNEL);
256: if (!page)
257: return -ENOMEM;
258:
259: uport = uart_port_ref_lock(state, &flags);
260: if (!state->port.xmit_buf) {
261: state->port.xmit_buf = (unsigned char *)page;
262: kfifo_init(&state->port.xmit_fifo, state->port.xmit_buf,
263: PAGE_SIZE);
264: uart_port_unlock_deref(uport, flags);
265: } else {
266: uart_port_unlock_deref(uport, flags);
267: /*
268: * Do not free() the page under the port lock, see
269: * uart_free_xmit_buf().
270: */
271: free_page(page);
272: }
273:
274: return 0;
275: }
SourceFile:drivers/tty/serial/serial_core.c]
|
| 38/2 |
2026/05/23 09:46 |
llm |
expert |
0m
Model:
Tokens:
input: 49050
output: 48
thoughts: 12
Thoughts: Okay, here's my attempt at summarizing those thoughts from an expert's perspective, using a first-person perspective:
**Deep Dive on Resource Management: Freeing Transmit Buffers**
Alright, so I'm looking at this code, and the first thing that pops into my head is a very specific function: `uart_free_xmit_buf`. I'm immediately thinking, "Okay, that function *should* be handling the cleanup of transmit buffers." But I need to really understand the context. Is there an issue I need to worry about?
This leads to a more general thought. How robust is the buffer management around transmitting data? Is this function called often enough? Does it protect against errors?
So, this prompts me to perform a mental audit of the buffer management system. Are we dealing with dynamic allocation, and if so, how are we preventing memory leaks? Is there a corresponding `uart_alloc_xmit_buf` or similar function? What's the thread safety like here? Do we have race conditions if multiple threads are writing to the buffer? Are there any potential deadlocks?
I need to quickly assess how efficiently this `uart_free_xmit_buf` is being *used* as well. Are we freeing the buffers as soon as they're no longer needed, or are there delays that could lead to resource contention or even buffer overflows in high-throughput scenarios? This may or may not be relevant depending on how fast or slow this port is.
Ultimately, I'm thinking about the bigger picture: resource allocation, deallocation, and the potential pitfalls around transmit buffer management in this specific UART implementation. `uart_free_xmit_buf` is just a key point for further analysis and, depending on the context of the code, maybe it is a place for an urgent issue to be uncovered.
|
| 39/2 |
2026/05/23 09:46 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/serial/serial_core.c IncludeLines:true Name:uart_free_xmit_buf]
Results: map[SourceCode: 277: static void uart_free_xmit_buf(struct tty_port *port)
278: {
279: struct uart_state *state = container_of(port, struct uart_state, port);
280: struct uart_port *uport;
281: unsigned long flags;
282: char *xmit_buf;
283:
284: /*
285: * Do not free() the transmit buffer page under the port lock since
286: * this can create various circular locking scenarios. For instance,
287: * console driver may need to allocate/free a debug object, which
288: * can end up in printk() recursion.
289: */
290: uport = uart_port_ref_lock(state, &flags);
291: xmit_buf = port->xmit_buf;
292: port->xmit_buf = NULL;
293: INIT_KFIFO(port->xmit_fifo);
294: uart_port_unlock_deref(uport, flags);
295:
296: free_page((unsigned long)xmit_buf);
297: }
SourceFile:drivers/tty/serial/serial_core.c]
|
| 40/2 |
2026/05/23 09:46 |
llm |
expert |
1m
Model:
Tokens:
input: 49865
output: 19
thoughts: 32
Thoughts: Okay, here's my interpretation of that thought process, assuming I'm an expert in embedded systems/kernel development:
**Initial Thoughts on `INIT_KFIFO`**
Right, *that* line's being hit. `INIT_KFIFO(port->xmit_fifo)`... Okay, so a kfifo's being initialized for the transmit side of the `port` structure. This is pretty standard stuff, likely dealing with a hardware serial port or a similar device. The `xmit_fifo` suggests it's the buffer where outgoing data will be staged before being sent. Let's dig into what `INIT_KFIFO` actually *does*. I need to quickly refresh my memory on the details to be sure it's set up correctly: size, pointers, memory allocation (or lack thereof), potential synchronization issues⦠is this a static or dynamic initialization? I need to know how this impacts interrupt handling and data flow from the driver. Right, time to verify the mechanics...
|
| 41/2 |
2026/05/23 09:47 |
tool |
grepper |
0m
Args: map[Expression:define INIT_KFIFO]
Results: map[Output:include/linux/kfifo.h=100=struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PTR(unsigned char, 2, void);
--
include/linux/kfifo.h-128- */
include/linux/kfifo.h:129:#define INIT_KFIFO(fifo) \
include/linux/kfifo.h-130-(void)({ \
]
|
| 42/2 |
2026/05/23 09:47 |
llm |
expert |
0m
Model:
Tokens:
input: 50234
output: 19
thoughts: 21
Thoughts: Here's my take on those thoughts, tailored for an expert audience:
**Diving into the Kernel FIFO Initialization**
Okay, so I'm thinking, let's refresh our memory on the `INIT_KFIFO` macro within `include/linux/kfifo.h`. It's been a while since I've scrutinized this particular bit of code. I'm keen to understand precisely how we're setting up the initial state of the kernel FIFO. Knowing this initialization is crucial; it sets the stage for everything that follows in its use. I need to be sure on the underlying memory layout, specifically, what's being initialized and what assumptions are baked in. I will pay careful attention to the nuances between `kf_head`, `kf_tail`, `mask`, and the `buf` pointer. Let me get the actual definition...
|
| 43/2 |
2026/05/23 09:47 |
tool |
grepper |
0m
Args: map[Expression:define INIT_KFIFO]
Results: map[Output:include/linux/kfifo.h=100=struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PTR(unsigned char, 2, void);
--
include/linux/kfifo.h-128- */
include/linux/kfifo.h:129:#define INIT_KFIFO(fifo) \
include/linux/kfifo.h-130-(void)({ \
]
|
| 44/2 |
2026/05/23 09:47 |
llm |
expert |
0m
Model:
Tokens:
input: 50561
output: 19
thoughts: 21
Thoughts: Here's a summary of my thought process, as requested:
**Diving into the Kernel FIFO Implementation**
Okay, time to get my hands dirty. I need to understand the kernel's circular FIFO implementation. Specifically, I'm going to navigate to `include/linux/kfifo.h` and focus around line 129. I expect this to be where the core data structure or perhaps an initialization function is defined. I'm looking for the foundational elements: the internal buffer, read and write pointers, and maybe some associated metadata. I want to see how they've handled the wraparound logic in the circular buffer; that's always the trickiest part. Are they using modulo arithmetic directly, or some bitwise trickery for powers of two? And are there any interesting optimizations in play? Let's get to it.
|
| 45/2 |
2026/05/23 09:47 |
tool |
grepper |
0m
Args: map[Expression:define INIT_KFIFO]
Results: map[Output:include/linux/kfifo.h=100=struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PTR(unsigned char, 2, void);
--
include/linux/kfifo.h-128- */
include/linux/kfifo.h:129:#define INIT_KFIFO(fifo) \
include/linux/kfifo.h-130-(void)({ \
]
|
| 46/2 |
2026/05/23 09:47 |
llm |
expert |
0m
Model:
Tokens:
input: 50887
output: 41
thoughts: 577
Thoughts: **Debugging a Tricky UART Issue**
Okay, let's break this down. The problem seems to be an RCU stall, and it's all starting with how the UART is interacting with the line discipline and network traffic. First, `INIT_KFIFO` zeroes out `in`, `out`, and `mask`. So, if I understand correctly, `kfifo_avail` should return `mask + 1 - (in - out)`, which in this initialized state is `0 + 1 - 0 = 1`. Yes! `kfifo_avail` correctly reports an availability of 1.
That means `uart_write_room` is indeed returning 1. But then, `uart_write` fails, returning 0, because `xmit_buf` is NULL. This confirms my hypothesis. So it appears that the core issue is that `caif_serial` is setup on a tty, the tty closes triggering a release, but packets continue to arrive before the cleanup is completely done.
So, here's what's happening:
1. `caif_serial` is attached as a line discipline.
2. The tty closes which calls `ldisc_close` which schedules `ser_release_work`.
3. Before `ser_release_work` executes, the network device is still active.
4. A network sender (`aoe` or similar) sends data over the `caif` network device.
5. `caif_xmit` triggers `handle_tx`.
6. `handle_tx` calls `tty_write_room(tty)` which in turn calls `uart_write_room`.
7. `uart_write_room` then returns 1 (because `xmit_fifo` was reset by `uart_free_xmit_buf`). This is the crux.
8. `handle_tx` attempts to write one byte using `tty->ops->write`, which calls `uart_write`.
9. `uart_write` fails, returning 0, because `xmit_buf` is NULL.
10. `handle_tx` gets stuck in a loop, causing an RCU stall.
But... hang on. I need to be sure about the order of operations. Is `uart_free_xmit_buf` called *before* `ldisc_close`? Let's trace it... When a tty closes, `tty_release` is invoked. `tty_release` calls `tty_release_struct`, which then calls `tty_ldisc_release`. `tty_ldisc_release` triggers `tty_ldisc_close` which calls `disc->ops->close(tty)`. Next, `tty->ops->close(tty, filp)` is called. For serial ports, `uart_close` calls `tty_port_close`, which calls `tty_port_shutdown`. Inside that, `tty_port_shutdown` calls both `uart_port_shutdown` *and* `uart_free_xmit_buf`.
Wait a minute, `tty_ldisc_release` is called *before* `tty->ops->close`? I need to confirm this. I will look at the `tty_release` function in `drivers/tty/tty_io.c` to confirm the calling order. I think I've found the race.
|
| 47/2 |
2026/05/23 09:47 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/tty_io.c IncludeLines:true Name:tty_release]
Results: map[SourceCode:1697: /**
1698: * tty_release - vfs callback for close
1699: * @inode: inode of tty
1700: * @filp: file pointer for handle to tty
1701: *
1702: * Called the last time each file handle is closed that references this tty.
1703: * There may however be several such references.
1704: *
1705: * Locking:
1706: * Takes BKL. See tty_release_dev().
1707: *
1708: * Even releasing the tty structures is a tricky business. We have to be very
1709: * careful that the structures are all released at the same time, as interrupts
1710: * might otherwise get the wrong pointers.
1711: *
1712: * WSH 09/09/97: rewritten to avoid some nasty race conditions that could
1713: * lead to double frees or releasing memory still in use.
1714: */
1715: int tty_release(struct inode *inode, struct file *filp)
1716: {
1717: struct tty_struct *tty = file_tty(filp);
1718: struct tty_struct *o_tty = NULL;
1719: int do_sleep, final;
1720: int idx;
1721: long timeout = 0;
1722: int once = 1;
1723:
1724: if (tty_paranoia_check(tty, inode, __func__))
1725: return 0;
1726:
1727: tty_lock(tty);
1728: check_tty_count(tty, __func__);
1729:
1730: __tty_fasync(-1, filp, 0);
1731:
1732: idx = tty->index;
1733: if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
1734: tty->driver->subtype == PTY_TYPE_MASTER)
1735: o_tty = tty->link;
1736:
1737: if (tty_release_checks(tty, idx)) {
1738: tty_unlock(tty);
1739: return 0;
1740: }
1741:
1742: tty_debug_hangup(tty, "releasing (count=%d)\n", tty->count);
1743:
1744: if (tty->ops->close)
1745: tty->ops->close(tty, filp);
1746:
1747: /* If tty is pty master, lock the slave pty (stable lock order) */
1748: tty_lock_slave(o_tty);
1749:
1750: /*
1751: * Sanity check: if tty->count is going to zero, there shouldn't be
1752: * any waiters on tty->read_wait or tty->write_wait. We test the
1753: * wait queues and kick everyone out _before_ actually starting to
1754: * close. This ensures that we won't block while releasing the tty
1755: * structure.
1756: *
1757: * The test for the o_tty closing is necessary, since the master and
1758: * slave sides may close in any order. If the slave side closes out
1759: * first, its count will be one, since the master side holds an open.
1760: * Thus this test wouldn't be triggered at the time the slave closed,
1761: * so we do it now.
1762: */
1763: while (1) {
1764: do_sleep = 0;
1765:
1766: if (tty->count <= 1) {
1767: if (waitqueue_active(&tty->read_wait)) {
1768: wake_up_poll(&tty->read_wait, EPOLLIN);
1769: do_sleep++;
1770: }
1771: if (waitqueue_active(&tty->write_wait)) {
1772: wake_up_poll(&tty->write_wait, EPOLLOUT);
1773: do_sleep++;
1774: }
1775: }
1776: if (o_tty && o_tty->count <= 1) {
1777: if (waitqueue_active(&o_tty->read_wait)) {
1778: wake_up_poll(&o_tty->read_wait, EPOLLIN);
1779: do_sleep++;
1780: }
1781: if (waitqueue_active(&o_tty->write_wait)) {
1782: wake_up_poll(&o_tty->write_wait, EPOLLOUT);
1783: do_sleep++;
1784: }
1785: }
1786: if (!do_sleep)
1787: break;
1788:
1789: if (once) {
1790: once = 0;
1791: tty_warn(tty, "read/write wait queue active!\n");
1792: }
1793: schedule_timeout_killable(timeout);
1794: if (timeout < 120 * HZ)
1795: timeout = 2 * timeout + 1;
1796: else
1797: timeout = MAX_SCHEDULE_TIMEOUT;
1798: }
1799:
1800: if (o_tty) {
1801: if (--o_tty->count < 0) {
1802: tty_warn(tty, "bad slave count (%d)\n", o_tty->count);
1803: o_tty->count = 0;
1804: }
1805: }
1806: if (--tty->count < 0) {
1807: tty_warn(tty, "bad tty->count (%d)\n", tty->count);
1808: tty->count = 0;
1809: }
1810:
1811: /*
1812: * We've decremented tty->count, so we need to remove this file
1813: * descriptor off the tty->tty_files list; this serves two
1814: * purposes:
1815: * - check_tty_count sees the correct number of file descriptors
1816: * associated with this tty.
1817: * - do_tty_hangup no longer sees this file descriptor as
1818: * something that needs to be handled for hangups.
1819: */
1820: tty_del_file(filp);
1821:
1822: /*
1823: * Perform some housekeeping before deciding whether to return.
1824: *
1825: * If _either_ side is closing, make sure there aren't any
1826: * processes that still think tty or o_tty is their controlling
1827: * tty.
1828: */
1829: if (!tty->count) {
1830: read_lock(&tasklist_lock);
1831: session_clear_tty(tty->ctrl.session);
1832: if (o_tty)
1833: session_clear_tty(o_tty->ctrl.session);
1834: read_unlock(&tasklist_lock);
1835: }
1836:
1837: /* check whether both sides are closing ... */
1838: final = !tty->count && !(o_tty && o_tty->count);
1839:
1840: tty_unlock_slave(o_tty);
1841: tty_unlock(tty);
1842:
1843: /* At this point, the tty->count == 0 should ensure a dead tty
1844: * cannot be re-opened by a racing opener.
1845: */
1846:
1847: if (!final)
1848: return 0;
1849:
1850: tty_debug_hangup(tty, "final close\n");
1851:
1852: tty_release_struct(tty, idx);
1853: return 0;
1854: }
SourceFile:drivers/tty/tty_io.c]
|
| 48/2 |
2026/05/23 09:47 |
llm |
expert |
0m
Model:
Tokens:
input: 54620
output: 39
thoughts: 611
Thoughts: **Analyzing a Kernel Denial of Service Vulnerability**
Okay, so I've been tracing the execution flow, and I think I've found a critical issue. Line 1745 calls `tty->ops->close(tty, filp)`, and then `tty_release_struct` happens later at line 1852. Specifically, for serial ports, `tty->ops->close` boils down to `uart_close`, which frees the `xmit_buf`. Then `tty_release_struct` calls `tty_ldisc_release`, which in turn calls `ldisc_close`. The problem is that `xmit_buf` gets freed *before* the line discipline is closed!
This means there's a window of vulnerability. `xmit_buf` is NULL, but the line discipline is still active, and crucially, the network device is still up. If `aoe` sends a packet during this vulnerable window, `handle_tx` gets called. `handle_tx` calls `tty_write_room`, which, because `xmit_fifo` is reset, returns 1. However, since `xmit_buf` is now NULL, `tty->ops->write` returns 0. The disastrous result? `handle_tx` enters an infinite loop!
This is a clear denial of service; the infinite loop in a kernel thread (`aoe_tx0` or softirq) is going to cause an RCU stall. The question now is, is it exploitable? Since it's an infinite loop, it's definitely a DoS. But can it be triggered by an unprivileged user? The reproducer uses `openat(AT_FDCWD, "/dev/ttyS3", O_RDONLY)`, `ioctl(fd, TIOCSETD, N_CAIF)`, and `syz_mount_image` with `ocfs2`. I'm guessing `ocfs2` is triggering some network activity, maybe through `aoe`, or maybe `aoe` is already sending periodic discovery packets. Or perhaps `ocfs2` itself uses an `aoe` block device. Either way, the bug's in `caif_serial` and `serial_core`.
The crucial question for exploitability is access to `/dev/ttyS3`. Normally, `/dev/ttyS*` belongs to `root:dialout` with permissions `0660`. Unless the user is in the `dialout` group, they wouldn't have access. However, what about `/dev/ptmx`? Can an unprivileged user exploit this through a pseudo-terminal (pty) instead of a serial port? We need to investigate if pty's `tty->ops->write` (which is `pty_write`) is vulnerable as well.
|
| 49/2 |
2026/05/23 09:47 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/pty.c IncludeLines:true Name:pty_write]
Results: map[SourceCode: 109: static ssize_t pty_write(struct tty_struct *tty, const u8 *buf, size_t c)
110: {
111: struct tty_struct *to = tty->link;
112:
113: if (tty->flow.stopped || !c)
114: return 0;
115:
116: return tty_insert_flip_string_and_push_buffer(to->port, buf, c);
117: }
SourceFile:drivers/tty/pty.c]
|
| 50/2 |
2026/05/23 09:47 |
llm |
expert |
0m
Model:
Tokens:
input: 56045
output: 44
thoughts: 364
Thoughts: **Debugging a Serial Port Issue**
Okay, so I'm trying to figure out this serial port bug. My initial question is: does `pty_write` return 0 when the pty is closed? I need to understand the control flow, because when the pty closes, `pty_close` is the function that gets called. However, I know there's no `xmit_buf` associated with the pty. I need to understand that the root cause of this bug is specifically because `uart_write_room` returns 1 when `xmit_buf` is NULL, which causes `uart_write` to return 0 when `xmit_buf` is NULL. I think that I've narrowed this down to `serial_core.c`.
The bug seems specific to a serial port (`uart_port`), right? Now I need to consider the threat model. Can an unprivileged user even *open* a serial port? No, `/dev/ttyS*` is usually restricted. Hmm, but what if they use a virtual one, like a `ttyGS0` (the USB gadget serial) or something? Usually all serial ports are restricted, so that's probably not the vector.
Is there any other way to trigger this? I was wondering if a user namespace might help, but they still can't open `/dev/ttyS3` because they don't own the device node and can't even `mknod` a real device.
Ah, wait. The reproducer runs as root in syzkaller! Okay, so `openat(AT_FDCWD, "/dev/ttyS3", O_RDONLY)` *will* succeed in that environment. So it requires root or `dialout` group, but it's not accessible from unprivileged processes.
Wait, I think I've got it. Is the `N_CAIF` line discipline available to unprivileged users? I need to check `ioctl(fd, TIOCSETD, &ldisc)` because I think it needs `CAP_SYS_ADMIN`. I should check `tty_set_ldisc` in `drivers/tty/tty_io.c`.
|
| 51/2 |
2026/05/23 09:48 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/tty_io.c IncludeLines:true Name:tty_set_ldisc]
Results: map[SourceCode: 509: /**
510: * tty_set_ldisc - set line discipline
511: * @tty: the terminal to set
512: * @disc: the line discipline number
513: *
514: * Set the discipline of a tty line. Must be called from a process context. The
515: * ldisc change logic has to protect itself against any overlapping ldisc
516: * change (including on the other end of pty pairs), the close of one side of a
517: * tty/pty pair, and eventually hangup.
518: */
519: int tty_set_ldisc(struct tty_struct *tty, int disc)
520: {
521: int retval;
522: struct tty_ldisc *old_ldisc, *new_ldisc;
523:
524: new_ldisc = tty_ldisc_get(tty, disc);
525: if (IS_ERR(new_ldisc))
526: return PTR_ERR(new_ldisc);
527:
528: tty_lock(tty);
529: retval = tty_ldisc_lock(tty, 5 * HZ);
530: if (retval)
531: goto err;
532:
533: if (!tty->ldisc) {
534: retval = -EIO;
535: goto out;
536: }
537:
538: /* Check the no-op case */
539: if (tty->ldisc->ops->num == disc)
540: goto out;
541:
542: if (test_bit(TTY_HUPPED, &tty->flags)) {
543: /* We were raced by hangup */
544: retval = -EIO;
545: goto out;
546: }
547:
548: if (tty->ops->ldisc_ok) {
549: retval = tty->ops->ldisc_ok(tty, disc);
550: if (retval)
551: goto out;
552: }
553:
554: old_ldisc = tty->ldisc;
555:
556: /* Shutdown the old discipline. */
557: tty_ldisc_close(tty, old_ldisc);
558:
559: /* Now set up the new line discipline. */
560: tty->ldisc = new_ldisc;
561: tty_set_termios_ldisc(tty, disc);
562:
563: retval = tty_ldisc_open(tty, new_ldisc);
564: if (retval < 0) {
565: /* Back to the old one or N_TTY if we can't */
566: tty_ldisc_put(new_ldisc);
567: tty_ldisc_restore(tty, old_ldisc);
568: }
569:
570: if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) {
571: down_read(&tty->termios_rwsem);
572: tty->ops->set_ldisc(tty);
573: up_read(&tty->termios_rwsem);
574: }
575:
576: /*
577: * At this point we hold a reference to the new ldisc and a
578: * reference to the old ldisc, or we hold two references to
579: * the old ldisc (if it was restored as part of error cleanup
580: * above). In either case, releasing a single reference from
581: * the old ldisc is correct.
582: */
583: new_ldisc = old_ldisc;
584: out:
585: tty_ldisc_unlock(tty);
586:
587: /*
588: * Restart the work queue in case no characters kick it off. Safe if
589: * already running
590: */
591: tty_buffer_restart_work(tty->port);
592: err:
593: tty_ldisc_put(new_ldisc); /* drop the extra reference */
594: tty_unlock(tty);
595: return retval;
596: }
SourceFile:drivers/tty/tty_ldisc.c]
|
| 52/2 |
2026/05/23 09:48 |
llm |
expert |
0m
Model:
Tokens:
input: 58242
output: 42
thoughts: 59
Thoughts: Okay, let me think this through.
**Investigating a Potential Security Oversight in TTY Line Discipline Handling**
Hmm, this is curious. I was under the impression that the `tty_set_ldisc` function, which is, of course, critical for setting the line discipline in a TTY, included a check for `capable(CAP_SYS_ADMIN)`. That would seem to be the obvious and necessary security measure to prevent unauthorized line discipline changes. But, on closer inspection, it doesn't. That's... concerning. Where then is this permission check?
Ah! I see now. The real action doesn't reside directly within `tty_set_ldisc`. Instead, `ioctl(fd, TIOCSETD, &ldisc)` is the system call interface responsible for driving the change. And that calls `tiocsetd`, which is actually defined in `drivers/tty/tty_io.c`. This is where the security check should live. I'll need to double-check that `tiocsetd` function to ensure the necessary permissions checks are present. I'd hate to have a privilege escalation vulnerability on my hands.
|
| 53/2 |
2026/05/23 09:48 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/tty_io.c IncludeLines:true Name:tiocsetd]
Results: map[SourceCode:2412: /**
2413: * tiocsetd - set line discipline
2414: * @tty: tty device
2415: * @p: pointer to user data
2416: *
2417: * Set the line discipline according to user request.
2418: *
2419: * Locking: see tty_set_ldisc(), this function is just a helper
2420: */
2421: static int tiocsetd(struct tty_struct *tty, int __user *p)
2422: {
2423: int disc;
2424: int ret;
2425:
2426: if (get_user(disc, p))
2427: return -EFAULT;
2428:
2429: ret = tty_set_ldisc(tty, disc);
2430:
2431: return ret;
2432: }
SourceFile:drivers/tty/tty_io.c]
|
| 54/2 |
2026/05/23 09:48 |
llm |
expert |
0m
Model:
Tokens:
input: 58884
output: 46
thoughts: 82
Thoughts: **Investigating Line Discipline Security**
Okay, so the core idea here is, if someone gets access to a terminal, they can mess with its line discipline. That's the starting point. The question is, can a regular user, without any special privileges, actually *create* a terminal they can then manipulate? Specifically, can they get a pseudo-terminal? And, if they *can*, what are the implications?
The next step is to remember that `/dev/ptmx` is world-readable *and* world-writable. That's a huge clue! So, yes, an unprivileged user can open a pty using this device.
Now, the real question that comes to mind is: what can I *do* with that? Specifically, can I attach a `caif_serial` device to this newly-created pty? It would be interesting to learn if there are any restrictions, in the `caif_serial.c` code, that explicitly check the type of tty that is trying to be attached. If there aren't, then we could potentially gain some level of control we aren't supposed to have. Let's dig into that source code and find out!
|
| 55/2 |
2026/05/23 09:48 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/caif/caif_serial.c IncludeLines:true Name:ldisc_open]
Results: map[SourceCode: 305: static int ldisc_open(struct tty_struct *tty)
306: {
307: struct ser_device *ser;
308: struct net_device *dev;
309: char name[64];
310: int result;
311:
312: /* No write no play */
313: if (tty->ops->write == NULL)
314: return -EOPNOTSUPP;
315: if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG))
316: return -EPERM;
317:
318: /* release devices to avoid name collision */
319: ser_release(NULL);
320:
321: result = snprintf(name, sizeof(name), "cf%s", tty->name);
322: if (result >= IFNAMSIZ)
323: return -EINVAL;
324: dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN,
325: caifdev_setup);
326: if (!dev)
327: return -ENOMEM;
328:
329: ser = netdev_priv(dev);
330: ser->tty = tty_kref_get(tty);
331: ser->dev = dev;
332: debugfs_init(ser, tty);
333: tty->receive_room = 4096;
334: tty->disc_data = ser;
335: set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
336: rtnl_lock();
337: result = register_netdevice(dev);
338: if (result) {
339: tty_kref_put(tty);
340: rtnl_unlock();
341: free_netdev(dev);
342: return -ENODEV;
343: }
344:
345: spin_lock(&ser_lock);
346: list_add(&ser->node, &ser_list);
347: spin_unlock(&ser_lock);
348: rtnl_unlock();
349: netif_stop_queue(dev);
350: update_tty_status(ser);
351: return 0;
352: }
SourceFile:drivers/net/caif/caif_serial.c]
|
| 56/2 |
2026/05/23 09:48 |
llm |
expert |
0m
Model:
Tokens:
input: 59993
output: 41
thoughts: 252
Thoughts: **Analyzing the Line Discipline Security Implications**
Okay, so looking at this `ldisc_open` function, it's immediately clear that it's using `capable(CAP_SYS_ADMIN)` or `capable(CAP_SYS_TTY_CONFIG)`. Right, that's the gatekeeper. Meaning a completely unprivileged user *definitely* can't attach an `N_CAIF` line discipline. Simple enough.
Hold on, though... it's using the global `capable()` check, not `ns_capable()`. That's a crucial distinction. If it *was* using `ns_capable()`, a user within a user namespace could potentially exploit this. But since it's `capable()`, it means it's requiring global privileges, a user with `CAP_SYS_ADMIN` or `CAP_SYS_TTY_CONFIG` in the *initial* user namespace. That solidifies it: an unprivileged user can't exploit this, not even inside a user namespace. It's safe!
Now, the important question is: is this the only way to trigger the issue, or can this bug be exploited through a different vector?
The problem's cause is in `caif_serial.c`'s `handle_tx` function, which has an infinite loop stemming from `tty_write_room` returning a value greater than 0, while `tty->ops->write` returns 0. That is the vulnerability.
So, are there any other line disciplines with a similar potential? Let's take a look at `slip` (SLIP) or `ppp_async` (PPP). I need to check if there are similar checks within their associated line discipline implementation.
|
| 57/2 |
2026/05/23 09:48 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/slip/slip.c IncludeLines:true Name:slip_open]
Results: map[SourceCode: 788: static int slip_open(struct tty_struct *tty)
789: {
790: struct slip *sl;
791: int err;
792:
793: if (!capable(CAP_NET_ADMIN))
794: return -EPERM;
795:
796: if (tty->ops->write == NULL)
797: return -EOPNOTSUPP;
798:
799: /* RTnetlink lock is misused here to serialize concurrent
800: opens of slip channels. There are better ways, but it is
801: the simplest one.
802: */
803: rtnl_lock();
804:
805: /* Collect hanged up channels. */
806: sl_sync();
807:
808: sl = tty->disc_data;
809:
810: err = -EEXIST;
811: /* First make sure we're not already connected. */
812: if (sl && sl->magic == SLIP_MAGIC)
813: goto err_exit;
814:
815: /* OK. Find a free SLIP channel to use. */
816: err = -ENFILE;
817: sl = sl_alloc();
818: if (sl == NULL)
819: goto err_exit;
820:
821: sl->tty = tty;
822: tty->disc_data = sl;
823: sl->pid = current->pid;
824:
825: if (!test_bit(SLF_INUSE, &sl->flags)) {
826: /* Perform the low-level SLIP initialization. */
827: err = sl_alloc_bufs(sl, SL_MTU);
828: if (err)
829: goto err_free_chan;
830:
831: set_bit(SLF_INUSE, &sl->flags);
832:
833: err = register_netdevice(sl->dev);
834: if (err)
835: goto err_free_bufs;
836: }
837:
838: #ifdef CONFIG_SLIP_SMART
839: if (sl->keepalive) {
840: sl->keepalive_timer.expires = jiffies + sl->keepalive * HZ;
841: add_timer(&sl->keepalive_timer);
842: }
843: if (sl->outfill) {
844: sl->outfill_timer.expires = jiffies + sl->outfill * HZ;
845: add_timer(&sl->outfill_timer);
846: }
847: #endif
848:
849: /* Done. We have linked the TTY line to a channel. */
850: rtnl_unlock();
851: tty->receive_room = 65536; /* We don't flow control */
852:
853: /* TTY layer expects 0 on success */
854: return 0;
855:
856: err_free_bufs:
857: sl_free_bufs(sl);
858:
859: err_free_chan:
860: sl->tty = NULL;
861: tty->disc_data = NULL;
862: clear_bit(SLF_INUSE, &sl->flags);
863: sl_free_netdev(sl->dev);
864: /* do not call free_netdev before rtnl_unlock */
865: rtnl_unlock();
866: free_netdev(sl->dev);
867: return err;
868:
869: err_exit:
870: rtnl_unlock();
871:
872: /* Count references from TTY module */
873: return err;
874: }
SourceFile:drivers/net/slip/slip.c]
|
| 58/2 |
2026/05/23 09:48 |
llm |
expert |
1m
Model:
Tokens:
input: 61856
output: 48
thoughts: 25
Thoughts: Okay, here's my interpretation of those thoughts, tailored for an expert audience, presented in the first person:
**Kernel Security Considerations: `slip_open` and `ppp_async`**
Alright, let me think this through. I see the kernel's `slip_open` function is checking for `CAP_NET_ADMIN` capabilities. Makes sense; that's the standard guardrail for network configuration functions. It's a fundamental security measure, preventing unauthorized processes from mucking around with network interfaces. We want to ensure only privileged users can initiate network operations.
But then my mind goes to the broader picture. What about `ppp_async`? Now, that's where things get interesting. Is `ppp_async` also rigorously checking permissions, or are there potential bypasses or subtle vulnerabilities related to its asynchronous nature? I need to analyze its security model with respect to capability checks and potential privilege escalation vectors. Perhaps there is a risk of this function being exploited to bypass the access controls implemented by `slip_open`. This would mean any code relying on `slip_open` would then be rendered useless for security. That needs a deeper dive.
|
| 59/2 |
2026/05/23 09:49 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/ppp/ppp_async.c IncludeLines:true Name:ppp_asynctty_open]
Results: map[SourceCode: 151: /*
152: * Called when a tty is put into PPP line discipline. Called in process
153: * context.
154: */
155: static int
156: ppp_asynctty_open(struct tty_struct *tty)
157: {
158: struct asyncppp *ap;
159: int err;
160: int speed;
161:
162: if (tty->ops->write == NULL)
163: return -EOPNOTSUPP;
164:
165: err = -ENOMEM;
166: ap = kzalloc(sizeof(*ap), GFP_KERNEL);
167: if (!ap)
168: goto out;
169:
170: /* initialize the asyncppp structure */
171: ap->tty = tty;
172: ap->mru = PPP_MRU;
173: spin_lock_init(&ap->xmit_lock);
174: spin_lock_init(&ap->recv_lock);
175: ap->xaccm[0] = ~0U;
176: ap->xaccm[3] = 0x60000000U;
177: ap->raccm = ~0U;
178: ap->optr = ap->obuf;
179: ap->olim = ap->obuf;
180: ap->lcp_fcs = -1;
181:
182: skb_queue_head_init(&ap->rqueue);
183: tasklet_setup(&ap->tsk, ppp_async_process);
184:
185: refcount_set(&ap->refcnt, 1);
186: init_completion(&ap->dead);
187:
188: ap->chan.private = ap;
189: ap->chan.ops = &async_ops;
190: ap->chan.mtu = PPP_MRU;
191: speed = tty_get_baud_rate(tty);
192: ap->chan.speed = speed;
193: err = ppp_register_channel(&ap->chan);
194: if (err)
195: goto out_free;
196:
197: tty->disc_data = ap;
198: tty->receive_room = 65536;
199: return 0;
200:
201: out_free:
202: kfree(ap);
203: out:
204: return err;
205: }
SourceFile:drivers/net/ppp/ppp_async.c]
|
| 60/2 |
2026/05/23 09:49 |
llm |
expert |
0m
Model:
Tokens:
input: 62974
output: 45
thoughts: 75
Thoughts: Okay, here's what's running through my mind as I analyze this:
**Unveiling a Potential Security Flaw in PPP Handling**
Alright, this is interesting. It seems like the `ppp_asynctty_open` function is skipping a crucial security check: `capable()`. That's a red flag immediately. What that means is, any user, even those without elevated privileges, can potentially open a Pseudo-Terminal (pty) and then manipulate its line discipline to `N_PPP`. This is not good at all. We could have a privilege escalation vulnerability on our hands.
Now, my next instinct is to see if this isn't an isolated incident. Is this a systemic issue? Let me check quickly and see if `ppp_async` has the exact same flaw. Let's delve into the `ppp_async` code. Let's check `ppp_async_process` or `ppp_async_push` right away, those are the functions handling the data. We need to see if it makes the same oversight. This could be a significant security blind spot.
|
| 61/2 |
2026/05/23 09:49 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/ppp/ppp_async.c IncludeLines:true Name:ppp_async_push]
Results: map[SourceCode: 638: /*
639: * Push as much data as possible out to the tty.
640: */
641: static int
642: ppp_async_push(struct asyncppp *ap)
643: {
644: int avail, sent, done = 0;
645: struct tty_struct *tty = ap->tty;
646: int tty_stuffed = 0;
647:
648: /*
649: * We can get called recursively here if the tty write
650: * function calls our wakeup function. This can happen
651: * for example on a pty with both the master and slave
652: * set to PPP line discipline.
653: * We use the XMIT_BUSY bit to detect this and get out,
654: * leaving the XMIT_WAKEUP bit set to tell the other
655: * instance that it may now be able to write more now.
656: */
657: if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
658: return 0;
659: spin_lock_bh(&ap->xmit_lock);
660: for (;;) {
661: if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
662: tty_stuffed = 0;
663: if (!tty_stuffed && ap->optr < ap->olim) {
664: avail = ap->olim - ap->optr;
665: set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
666: sent = tty->ops->write(tty, ap->optr, avail);
667: if (sent < 0)
668: goto flush; /* error, e.g. loss of CD */
669: ap->optr += sent;
670: if (sent < avail)
671: tty_stuffed = 1;
672: continue;
673: }
674: if (ap->optr >= ap->olim && ap->tpkt) {
675: if (ppp_async_encode(ap)) {
676: /* finished processing ap->tpkt */
677: clear_bit(XMIT_FULL, &ap->xmit_flags);
678: done = 1;
679: }
680: continue;
681: }
682: /*
683: * We haven't made any progress this time around.
684: * Clear XMIT_BUSY to let other callers in, but
685: * after doing so we have to check if anyone set
686: * XMIT_WAKEUP since we last checked it. If they
687: * did, we should try again to set XMIT_BUSY and go
688: * around again in case XMIT_BUSY was still set when
689: * the other caller tried.
690: */
691: clear_bit(XMIT_BUSY, &ap->xmit_flags);
692: /* any more work to do? if not, exit the loop */
693: if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) ||
694: (!tty_stuffed && ap->tpkt)))
695: break;
696: /* more work to do, see if we can do it now */
697: if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
698: break;
699: }
700: spin_unlock_bh(&ap->xmit_lock);
701: return done;
702:
703: flush:
704: clear_bit(XMIT_BUSY, &ap->xmit_flags);
705: if (ap->tpkt) {
706: kfree_skb(ap->tpkt);
707: ap->tpkt = NULL;
708: clear_bit(XMIT_FULL, &ap->xmit_flags);
709: done = 1;
710: }
711: ap->optr = ap->olim;
712: spin_unlock_bh(&ap->xmit_lock);
713: return done;
714: }
SourceFile:drivers/net/ppp/ppp_async.c]
|
| 62/2 |
2026/05/23 09:49 |
llm |
expert |
0m
Model:
Tokens:
input: 64613
output: 49
thoughts: 295
Thoughts: **Analyzing the Asynchronous PPP Push Function**
Okay, let me think this through. `ppp_async_push`... I need to understand this write path. Here's what's happening. First, the code checks if there's data to send (`!tty_stuffed && ap->optr < ap->olim`). If there is, it calculates how much data is available (`avail`). Then, it signals a write wakeup (`set_bit(TTY_DO_WRITE_WAKEUP)`) and *tries* to write using `tty->ops->write`. The crucial bit: what if `tty->ops->write` *fails* and returns 0?
I see it now. If `write` returns 0, then `sent` *is* 0, and `ap->optr` doesn't advance. Critically, since `avail` is greater than 0, the check `sent < avail` *is* true, so `tty_stuffed` gets set to 1! That's the key.
So, in the next iteration, since `tty_stuffed` is now 1, *the write is skipped*. The code then checks `ap->optr >= ap->olim`. Since nothing was written, it *is* false. It then clears `XMIT_BUSY` and breaks out of the loop.
Therefore, `ppp_async_push` *does not* get stuck in an infinite loop if `write` returns zero. The `tty_stuffed` flag prevents it from repeatedly calling `write` when the underlying device can't accept any data. I was concerned about this. But the code does handle the case of `write` returning zero correctly.
Now, I need to consider `n_hdlc`...
|
| 63/2 |
2026/05/23 09:49 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/n_hdlc.c IncludeLines:true Name:n_hdlc_send_frames]
Results: map[SourceCode: 255: /**
256: * n_hdlc_send_frames - send frames on pending send buffer list
257: * @n_hdlc: pointer to ldisc instance data
258: * @tty: pointer to tty instance data
259: *
260: * Send frames on pending send buffer list until the driver does not accept a
261: * frame (busy) this function is called after adding a frame to the send buffer
262: * list and by the tty wakeup callback.
263: */
264: static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
265: {
266: struct n_hdlc_buf *tbuf;
267: ssize_t actual;
268:
269: check_again:
270: scoped_guard(spinlock_irqsave, &n_hdlc->tx_buf_list.spinlock) {
271: if (n_hdlc->tbusy) {
272: n_hdlc->woke_up = true;
273: return;
274: }
275: n_hdlc->tbusy = true;
276: n_hdlc->woke_up = false;
277: }
278:
279: tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
280: while (tbuf) {
281: pr_debug("sending frame %p, count=%zu\n", tbuf, tbuf->count);
282:
283: /* Send the next block of data to device */
284: set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
285: actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
286:
287: /* rollback was possible and has been done */
288: if (actual == -ERESTARTSYS) {
289: n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
290: break;
291: }
292: /* if transmit error, throw frame away by */
293: /* pretending it was accepted by driver */
294: if (actual < 0)
295: actual = tbuf->count;
296:
297: if (actual == tbuf->count) {
298: pr_debug("frame %p completed\n", tbuf);
299:
300: /* free current transmit buffer */
301: n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
302:
303: /* wait up sleeping writers */
304: wake_up_interruptible(&tty->write_wait);
305:
306: /* get next pending transmit buffer */
307: tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
308: } else {
309: pr_debug("frame %p pending\n", tbuf);
310:
311: /*
312: * the buffer was not accepted by driver,
313: * return it back into tx queue
314: */
315: n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
316: break;
317: }
318: }
319:
320: if (!tbuf)
321: clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
322:
323: /* Clear the re-entry flag */
324: scoped_guard(spinlock_irqsave, &n_hdlc->tx_buf_list.spinlock)
325: n_hdlc->tbusy = false;
326:
327: if (n_hdlc->woke_up)
328: goto check_again;
329: } /* end of n_hdlc_send_frames() */
SourceFile:drivers/tty/n_hdlc.c]
|
| 64/2 |
2026/05/23 09:49 |
llm |
expert |
0m
Model:
Tokens:
input: 66578
output: 43
thoughts: 148
Thoughts: Okay, let me break this down.
**HDLC Frame Transmission Concerns**
Right, so I'm looking at this `n_hdlc_send_frames` function. The key is in how it handles writing frames to the tty. Specifically, it uses `tty->ops->write()` to send the frame data (`tbuf->buf`) with a size of `tbuf->count`. The logic hinges on the return value of that write operation, `actual`.
If `actual` equals `tbuf->count`, all the data was accepted by the driver β perfect, we move on. But, *critically*, if `actual` is *not* equal to `tbuf->count*, and this looks like the crucial point here, then the code *returns* that frame buffer to the transmit queue. Crucially, I see that the code exits the loop.
So, if `actual` is `0` the code breaks which prevents an infinite loop. Excellent.
Now, I need to check how `n_gsm` works.
|
| 65/2 |
2026/05/23 09:49 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/n_gsm.c IncludeLines:true Name:gsm_data_kick]
Results: map[SourceCode:1007: /**
1008: * gsm_data_kick - poke the queue
1009: * @gsm: GSM Mux
1010: *
1011: * The tty device has called us to indicate that room has appeared in
1012: * the transmit queue. Ram more data into the pipe if we have any.
1013: * If we have been flow-stopped by a CMD_FCOFF, then we can only
1014: * send messages on DLCI0 until CMD_FCON. The caller must hold
1015: * the gsm tx lock.
1016: */
1017: static int gsm_data_kick(struct gsm_mux *gsm)
1018: {
1019: struct gsm_msg *msg, *nmsg;
1020: struct gsm_dlci *dlci;
1021: int ret;
1022:
1023: clear_bit(TTY_DO_WRITE_WAKEUP, &gsm->tty->flags);
1024:
1025: /* Serialize control messages and control channel messages first */
1026: list_for_each_entry_safe(msg, nmsg, &gsm->tx_ctrl_list, list) {
1027: if (gsm->constipated && !gsm_is_flow_ctrl_msg(msg))
1028: continue;
1029: ret = gsm_send_packet(gsm, msg);
1030: switch (ret) {
1031: case -ENOSPC:
1032: return -ENOSPC;
1033: case -ENODEV:
1034: /* ldisc not open */
1035: gsm->tx_bytes -= msg->len;
1036: list_del(&msg->list);
1037: kfree(msg);
1038: continue;
1039: default:
1040: if (ret >= 0) {
1041: list_del(&msg->list);
1042: kfree(msg);
1043: }
1044: break;
1045: }
1046: }
1047:
1048: if (gsm->constipated)
1049: return -EAGAIN;
1050:
1051: /* Serialize other channels */
1052: if (list_empty(&gsm->tx_data_list))
1053: return 0;
1054: list_for_each_entry_safe(msg, nmsg, &gsm->tx_data_list, list) {
1055: dlci = gsm->dlci[msg->addr];
1056: /* Send only messages for DLCIs with valid state */
1057: if (dlci->state != DLCI_OPEN) {
1058: gsm->tx_bytes -= msg->len;
1059: list_del(&msg->list);
1060: kfree(msg);
1061: continue;
1062: }
1063: ret = gsm_send_packet(gsm, msg);
1064: switch (ret) {
1065: case -ENOSPC:
1066: return -ENOSPC;
1067: case -ENODEV:
1068: /* ldisc not open */
1069: gsm->tx_bytes -= msg->len;
1070: list_del(&msg->list);
1071: kfree(msg);
1072: continue;
1073: default:
1074: if (ret >= 0) {
1075: list_del(&msg->list);
1076: kfree(msg);
1077: }
1078: break;
1079: }
1080: }
1081:
1082: return 1;
1083: }
SourceFile:drivers/tty/n_gsm.c]
|
| 66/2 |
2026/05/23 09:49 |
llm |
expert |
0m
Model:
Tokens:
input: 68110
output: 43
thoughts: 8
Thoughts: Okay, here's my attempt at summarizing the thought process, tailored for an expert audience, and written in the first person:
**Navigating `gsm_send_packet` - A Deep Dive**
Alright, let's break down this `gsm_send_packet` function. My initial concern, as always, is efficiency. I need to quickly ascertain how the packet data is being handled. Are we making unnecessary copies? Memory management is critical here, especially in embedded systems where resources are tight. I'm immediately looking for any potential for buffer overflows or underflows. The code needs to be robust, resistant to any malformed data coming in from, say, a less-than-trustworthy external source. I'm focusing on the data types used and size calculations β any integer overflows during the size calculations are a red flag. Also, how is the transmission handled in terms of queuing or buffering, and is that potentially blocking, or non-blocking? Are there proper error checks along the way; specifically, how are errors on the serial line treated, are retries used, and what are the time-out considerations? I need to analyze its interaction with the underlying serial driver. Does it handle flow control correctly? Are there any potential race conditions if other threads or interrupt handlers are interacting with the serial port simultaneously? Another question; can I use DMA?
Essentially, I want to ensure this core function is lean, secure, and reliable, handling the complexities of GSM packet transmission with grace and attention to detail. I'm also thinking about potential optimizations for speed and power consumption.
|
| 67/2 |
2026/05/23 09:49 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/n_gsm.c IncludeLines:true Name:gsm_send_packet]
Results: map[SourceCode: 937: /**
938: * gsm_send_packet - sends a single packet
939: * @gsm: GSM Mux
940: * @msg: packet to send
941: *
942: * The given packet is encoded and sent out. No memory is freed.
943: * The caller must hold the gsm tx lock.
944: */
945: static int gsm_send_packet(struct gsm_mux *gsm, struct gsm_msg *msg)
946: {
947: int len, ret;
948:
949:
950: if (gsm->encoding == GSM_BASIC_OPT) {
951: gsm->txframe[0] = GSM0_SOF;
952: memcpy(gsm->txframe + 1, msg->data, msg->len);
953: gsm->txframe[msg->len + 1] = GSM0_SOF;
954: len = msg->len + 2;
955: } else {
956: gsm->txframe[0] = GSM1_SOF;
957: len = gsm_stuff_frame(msg->data, gsm->txframe + 1, msg->len);
958: gsm->txframe[len + 1] = GSM1_SOF;
959: len += 2;
960: }
961:
962: if (debug & DBG_DATA)
963: gsm_hex_dump_bytes(__func__, gsm->txframe, len);
964: gsm_print_packet("-->", msg->addr, gsm->initiator, msg->ctrl, msg->data,
965: msg->len);
966:
967: ret = gsmld_output(gsm, gsm->txframe, len);
968: if (ret <= 0)
969: return ret;
970: /* FIXME: Can eliminate one SOF in many more cases */
971: gsm->tx_bytes -= msg->len;
972:
973: return 0;
974: }
SourceFile:drivers/tty/n_gsm.c]
|
| 68/2 |
2026/05/23 09:49 |
llm |
expert |
0m
Model:
Tokens:
input: 69130
output: 42
thoughts: 7
Thoughts: Okay, I'm ready. Let's see what we're working with. I need to understand this text and then paraphrase it as my own thought process, assuming I'm an expert in my field. I'll focus on the core meaning and the logic behind it, presenting it as if it's my internal reasoning. Let's go.
|
| 69/2 |
2026/05/23 09:49 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/n_gsm.c IncludeLines:true Name:gsmld_output]
Results: map[SourceCode:3515: static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len)
3516: {
3517: if (tty_write_room(gsm->tty) < len) {
3518: set_bit(TTY_DO_WRITE_WAKEUP, &gsm->tty->flags);
3519: return -ENOSPC;
3520: }
3521: if (debug & DBG_DATA)
3522: gsm_hex_dump_bytes(__func__, data, len);
3523: return gsm->tty->ops->write(gsm->tty, data, len);
3524: }
SourceFile:drivers/tty/n_gsm.c]
|
| 70/2 |
2026/05/23 09:49 |
llm |
expert |
0m
Model:
Tokens:
input: 69467
output: 44
thoughts: 315
Thoughts: **Analyzing Potential Loop Vulnerabilities**
Okay, so I'm digging into this potential loop issue. Let's see... if `tty->ops->write` comes back as 0, then `gsmld_output` returns 0, and then `gsm_send_packet` also returns 0. *Crucially*, the next thing `gsm_data_kick` does is treat that 0 as a success, nukes the message, and moves on. Bingo! That means it *doesn't* get stuck in an endless cycle. That's a relief; it won't loop forever.
So, where *does* the infinite loop happen? Ah, it's the `caif_serial` driver that's the culprit. However, it looks like you need either `CAP_SYS_ADMIN` or `CAP_SYS_TTY_CONFIG` to even *open* the damn thing. Wait a second, can a user namespace somehow get around that? I need to clarify: Does `capable()` check the *init* user namespace? Yes, it does. Therefore, that means a regular user namespace can't open that device. Alright, it's getting clearer: this isn't exploitable by just any unprivileged user.
Okay, let's step back and think. Are there other ways to trigger the infinite loop? Can we bypass `aoe` altogether and just write directly to the `caif` network device? Yes, any packet sent to the `caif` network device will definitely trigger `handle_tx`. The problem is that the `caif` network device only gets created when `ldisc_open` is called. And guess what? `ldisc_open` also requires `CAP_SYS_ADMIN` or `CAP_SYS_TTY_CONFIG`. So, no dice. An unprivileged user simply *can't* create that device in the first place. Therefore, it's looking less and less likely that an unprivileged user can trigger this.
Now, I wonder... is this bug specific to this line discipline, or is it broader? Let's broaden our view. We need to check other drivers. Okay, time to dive into `sixpack.c` and see if we can find something similar.
|
| 71/2 |
2026/05/23 09:50 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/hamradio/sixpack.c IncludeLines:true Name:sixpack_open]
Results: map[SourceCode: 497: /*
498: * Open the high-level part of the 6pack channel.
499: * This function is called by the TTY module when the
500: * 6pack line discipline is called for. Because we are
501: * sure the tty line exists, we only have to link it to
502: * a free 6pcack channel...
503: */
504: static int sixpack_open(struct tty_struct *tty)
505: {
506: char *xbuff = NULL;
507: struct net_device *dev;
508: struct sixpack *sp;
509: unsigned long len;
510: int err = 0;
511:
512: if (!capable(CAP_NET_ADMIN))
513: return -EPERM;
514: if (tty->ops->write == NULL)
515: return -EOPNOTSUPP;
516:
517: dev = alloc_netdev(sizeof(struct sixpack), "sp%d", NET_NAME_UNKNOWN,
518: sp_setup);
519: if (!dev) {
520: err = -ENOMEM;
521: goto out;
522: }
523:
524: sp = netdev_priv(dev);
525: sp->dev = dev;
526:
527: spin_lock_init(&sp->lock);
528: spin_lock_init(&sp->rxlock);
529:
530: /* !!! length of the buffers. MTU is IP MTU, not PACLEN! */
531:
532: len = dev->mtu * 2;
533:
534: xbuff = kmalloc(len + 4, GFP_KERNEL);
535: if (xbuff == NULL) {
536: err = -ENOBUFS;
537: goto out_free;
538: }
539:
540: spin_lock_bh(&sp->lock);
541:
542: sp->tty = tty;
543:
544: sp->xbuff = xbuff;
545:
546: sp->rcount = 0;
547: sp->rx_count = 0;
548: sp->rx_count_cooked = 0;
549: sp->xleft = 0;
550:
551: sp->flags = 0; /* Clear ESCAPE & ERROR flags */
552:
553: sp->duplex = 0;
554: sp->tx_delay = SIXP_TXDELAY;
555: sp->persistence = SIXP_PERSIST;
556: sp->slottime = SIXP_SLOTTIME;
557: sp->led_state = 0x60;
558: sp->status = 1;
559: sp->status1 = 1;
560: sp->status2 = 0;
561: sp->tx_enable = 0;
562:
563: netif_start_queue(dev);
564:
565: timer_setup(&sp->tx_t, sp_xmit_on_air, 0);
566:
567: timer_setup(&sp->resync_t, resync_tnc, 0);
568:
569: spin_unlock_bh(&sp->lock);
570:
571: /* Done. We have linked the TTY line to a channel. */
572: tty->disc_data = sp;
573: tty->receive_room = 65536;
574:
575: /* Now we're ready to register. */
576: err = register_netdev(dev);
577: if (err)
578: goto out_free;
579:
580: tnc_init(sp);
581:
582: return 0;
583:
584: out_free:
585: kfree(xbuff);
586:
587: free_netdev(dev);
588:
589: out:
590: return err;
591: }
SourceFile:drivers/net/hamradio/6pack.c]
|
| 72/2 |
2026/05/23 09:50 |
llm |
expert |
0m
Model:
Tokens:
input: 71633
output: 44
thoughts: 27
Thoughts: Here's my take on this, considering I'm supposed to be an expert:
**Investigating Network Capabilities and a Specific Driver**
Okay, so I'm looking at `sixpack_open`. The first thing that jumps out is that it's checking for `CAP_NET_ADMIN`. That makes perfect sense; opening a network-related function like this likely requires the ability to configure network interfaces, manage routing, or something similarly privileged. Makes me wonder what specifically it's doing with that capability. Is it setting up a tap device, configuring firewall rules, something else entirely? A deeper dive is probably needed to fully grasp the context.
My brain then immediately shifts gears and asks... what about `mkiss.c`? That's a driver, and I can almost smell the radio interface implications from here. Now, am I missing something? Are these two modules related, is `sixpack_open` dependent on or called by `mkiss.c`? It could be useful, or a complete red herring. I need to understand the connection, if there is one. The network setup is clearly important. I'll need to remember to check that relationship.
|
| 73/2 |
2026/05/23 09:50 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/hamradio/mkiss.c IncludeLines:true Name:mkiss_open]
Results: map[SourceCode: 688: static int mkiss_open(struct tty_struct *tty)
689: {
690: struct net_device *dev;
691: struct mkiss *ax;
692: int err;
693:
694: if (!capable(CAP_NET_ADMIN))
695: return -EPERM;
696: if (tty->ops->write == NULL)
697: return -EOPNOTSUPP;
698:
699: dev = alloc_netdev(sizeof(struct mkiss), "ax%d", NET_NAME_UNKNOWN,
700: ax_setup);
701: if (!dev) {
702: err = -ENOMEM;
703: goto out;
704: }
705:
706: ax = netdev_priv(dev);
707: ax->dev = dev;
708:
709: spin_lock_init(&ax->buflock);
710: refcount_set(&ax->refcnt, 1);
711: init_completion(&ax->dead);
712:
713: ax->tty = tty;
714: tty->disc_data = ax;
715: tty->receive_room = 65535;
716:
717: tty_driver_flush_buffer(tty);
718:
719: /* Restore default settings */
720: dev->type = ARPHRD_AX25;
721:
722: /* Perform the low-level AX25 initialization. */
723: err = ax_open(ax->dev);
724: if (err)
725: goto out_free_netdev;
726:
727: err = register_netdev(dev);
728: if (err)
729: goto out_free_buffers;
730:
731: /* after register_netdev() - because else printk smashes the kernel */
732: switch (crc_force) {
733: case 3:
734: ax->crcmode = CRC_MODE_SMACK;
735: printk(KERN_INFO "mkiss: %s: crc mode smack forced.\n",
736: ax->dev->name);
737: break;
738: case 2:
739: ax->crcmode = CRC_MODE_FLEX;
740: printk(KERN_INFO "mkiss: %s: crc mode flexnet forced.\n",
741: ax->dev->name);
742: break;
743: case 1:
744: ax->crcmode = CRC_MODE_NONE;
745: printk(KERN_INFO "mkiss: %s: crc mode disabled.\n",
746: ax->dev->name);
747: break;
748: case 0:
749: default:
750: crc_force = 0;
751: printk(KERN_INFO "mkiss: %s: crc mode is auto.\n",
752: ax->dev->name);
753: ax->crcmode = CRC_MODE_SMACK_TEST;
754: }
755: ax->crcauto = (crc_force ? 0 : 1);
756:
757: netif_start_queue(dev);
758:
759: /* Done. We have linked the TTY line to a channel. */
760: return 0;
761:
762: out_free_buffers:
763: kfree(ax->rbuff);
764: kfree(ax->xbuff);
765:
766: out_free_netdev:
767: free_netdev(dev);
768:
769: out:
770: return err;
771: }
SourceFile:drivers/net/hamradio/mkiss.c]
|
| 74/2 |
2026/05/23 09:50 |
llm |
expert |
1m
Model:
Tokens:
input: 73140
output: 42
thoughts: 69
Thoughts: Here's my summary, as I delve into this code:
**Capability Checks in Network Drivers**
Okay, so `mkiss_open` relies on `capable(CAP_NET_ADMIN)`. That's standard and expected. It's the gatekeeper, ensuring the caller has the necessary privileges to mess with network interfaces. Now, the question that pops into my head is, which drivers *don't* follow this pattern? I seem to recall that some of the older serial-over-network setups might have slipped through the cracks. Specifically, it looks like `ppp_async`, `n_hdlc`, and `n_gsm` are possible candidates. But, wait... does `n_gsm` truly *not* verify this? That seems a bit risky. I'd better double-check the `gsmld_open` function just to be absolutely sure. Gotta be thorough.
|
| 75/2 |
2026/05/23 09:51 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/n_gsm.c IncludeLines:true Name:gsmld_open]
Results: map[SourceCode:3685: static int gsmld_open(struct tty_struct *tty)
3686: {
3687: struct gsm_mux *gsm;
3688:
3689: if (!capable(CAP_NET_ADMIN))
3690: return -EPERM;
3691:
3692: if (tty->ops->write == NULL)
3693: return -EINVAL;
3694:
3695: /* Attach our ldisc data */
3696: gsm = gsm_alloc_mux();
3697: if (gsm == NULL)
3698: return -ENOMEM;
3699:
3700: tty->disc_data = gsm;
3701: tty->receive_room = 65536;
3702:
3703: /* Attach the initial passive connection */
3704: gsmld_attach_gsm(tty, gsm);
3705:
3706: /* The mux will not be activated yet, we wait for correct
3707: * configuration first.
3708: */
3709: if (gsm->encoding == GSM_BASIC_OPT)
3710: gsm->receive = gsm0_receive;
3711: else
3712: gsm->receive = gsm1_receive;
3713:
3714: return 0;
3715: }
SourceFile:drivers/tty/n_gsm.c]
|
| 76/2 |
2026/05/23 09:51 |
llm |
expert |
0m
Model:
Tokens:
input: 73871
output: 49
thoughts: 28
Thoughts: Okay, here's my take on those thoughts, framed as an expert's internal monologue:
**Investigating Network Capabilities**
Alright, I'm digging into this `gsmld_open` function. The first thing that pops out is that it's verifying `capable(CAP_NET_ADMIN)`. Makes sense; that's the core capability required to manipulate network interfaces and configurations, especially for something like GSM data links. It's a fundamental security check.
But then my mind jumps to `n_hdlc`. Thatβs the Network HDLC protocol. Is `gsmld_open` also concerned about it, or is this check isolated for GSM support? I need to understand the connection points, the data flow, and possible privilege escalation paths. Is `n_hdlc` a related dependency, or should I start my work there?
|
| 77/2 |
2026/05/23 09:51 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/tty/n_hdlc.c IncludeLines:true Name:n_hdlc_tty_open]
Results: map[SourceCode: 216: /**
217: * n_hdlc_tty_open - called when line discipline changed to n_hdlc
218: * @tty: pointer to tty info structure
219: *
220: * Returns 0 if success, otherwise error code
221: */
222: static int n_hdlc_tty_open(struct tty_struct *tty)
223: {
224: struct n_hdlc *n_hdlc = tty->disc_data;
225:
226: pr_debug("%s() called (device=%s)\n", __func__, tty->name);
227:
228: /* There should not be an existing table for this slot. */
229: if (n_hdlc) {
230: pr_err("%s: tty already associated!\n", __func__);
231: return -EEXIST;
232: }
233:
234: n_hdlc = n_hdlc_alloc();
235: if (!n_hdlc) {
236: pr_err("%s: n_hdlc_alloc failed\n", __func__);
237: return -ENFILE;
238: }
239:
240: INIT_WORK(&n_hdlc->write_work, n_hdlc_tty_write_work);
241: n_hdlc->tty_for_write_work = tty;
242: tty->disc_data = n_hdlc;
243: tty->receive_room = 65536;
244:
245: /* change tty_io write() to not split large writes into 8K chunks */
246: set_bit(TTY_NO_WRITE_SPLIT, &tty->flags);
247:
248: /* flush receive data from driver */
249: tty_driver_flush_buffer(tty);
250:
251: return 0;
252:
253: } /* end of n_tty_hdlc_open() */
SourceFile:drivers/tty/n_hdlc.c]
|
| 78/2 |
2026/05/23 09:51 |
llm |
expert |
0m
Model:
Tokens:
input: 74773
output: 44
thoughts: 636
Thoughts: **Analyzing the `caif_serial` Infinite Loop Bug**
Okay, so `n_hdlc_tty_open` doesn't do any capability checks, that's interesting. But, at least we know `n_hdlc` itself isn't the problem, thankfully. This infinite loop issue appears to be solely within `caif_serial`. The fact that `caif_serial` needs `CAP_SYS_ADMIN` or `CAP_SYS_TTY_CONFIG` in the init user namespace initially seemed like it would prevent any unprivileged users from triggering it.
However, I paused for a moment - what about a user with root privileges *within* a user namespace? But, `capable()` checks the `init_user_ns`, so even that wouldn't work. It's inaccessible from user namespaces - good.
The reproducer runs as root in syzkaller, which initially worried me. But, is it really exploitable, or just causing a problem? Thinking through it, this infinite loop happens in `handle_tx`, which is called from `ndo_start_xmit`. Right, `ndo_start_xmit` is called with either `rcu_read_lock_bh()` or similar, or just with bottom halves disabled. This means it's an RCU stall and soft lockup. So, it's a Denial of Service, *not* memory corruption. That's a relief, it's just an infinite loop because `tty_write_room` returns 1 and `tty->ops->write` returns 0.
But I still should check if there's *any* other way to trigger `handle_tx` without those specific CAPs. If root *already* attaches the `caif` line discipline, can an unprivileged user make this bug happen? If root attaches `N_CAIF` to, say, `/dev/ttyS3`, it creates a `caif` network device. Then root closes `/dev/ttyS3`.
Ah, if root closes `/dev/ttyS3`, `ldisc_close` gets called, which schedules `ser_release_work`. `ser_release_work` *should* unregister the network device. Okay, the critical window is between `uart_free_xmit_buf` and `unregister_netdevice`. If *during* that small window, a packet is sent to the `caif` network device, `handle_tx` is called.
Can an unprivileged user *send* a packet to that `caif` network device? If the network device is up, any user *can* send packets if they can route traffic to it. But `caif` is a specific protocol⦠Is it possible for an unprivileged user to send packets that end up in the `caif` device? Yes, if they send a packet to an IP address routed through the `caif` device!
But wait, `caif` devices are typically *not* IP devices, they're `ARPHRD_CAIF`. Okay, so, can an unprivileged user create a socket and *directly* send packets to it? Can `AF_CAIF` sockets even be created by unprivileged users? Let's check `caif_socket.c` and confirm that part.
|
| 79/2 |
2026/05/23 09:51 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:net/caif/caif_socket.c IncludeLines:true Name:caif_create]
Results: map[SourceCode:1017: static int caif_create(struct net *net, struct socket *sock, int protocol,
1018: int kern)
1019: {
1020: struct sock *sk = NULL;
1021: struct caifsock *cf_sk = NULL;
1022: static struct proto prot = {.name = "PF_CAIF",
1023: .owner = THIS_MODULE,
1024: .obj_size = sizeof(struct caifsock),
1025: .useroffset = offsetof(struct caifsock, conn_req.param),
1026: .usersize = sizeof_field(struct caifsock, conn_req.param)
1027: };
1028:
1029: if (!capable(CAP_SYS_ADMIN) && !capable(CAP_NET_ADMIN))
1030: return -EPERM;
1031: /*
1032: * The sock->type specifies the socket type to use.
1033: * The CAIF socket is a packet stream in the sense
1034: * that it is packet based. CAIF trusts the reliability
1035: * of the link, no resending is implemented.
1036: */
1037: if (sock->type == SOCK_SEQPACKET)
1038: sock->ops = &caif_seqpacket_ops;
1039: else if (sock->type == SOCK_STREAM)
1040: sock->ops = &caif_stream_ops;
1041: else
1042: return -ESOCKTNOSUPPORT;
1043:
1044: if (protocol < 0 || protocol >= CAIFPROTO_MAX)
1045: return -EPROTONOSUPPORT;
1046: /*
1047: * Set the socket state to unconnected. The socket state
1048: * is really not used at all in the net/core or socket.c but the
1049: * initialization makes sure that sock->state is not uninitialized.
1050: */
1051: sk = sk_alloc(net, PF_CAIF, GFP_KERNEL, &prot, kern);
1052: if (!sk)
1053: return -ENOMEM;
1054:
1055: cf_sk = container_of(sk, struct caifsock, sk);
1056:
1057: /* Store the protocol */
1058: sk->sk_protocol = (unsigned char) protocol;
1059:
1060: /* Initialize default priority for well-known cases */
1061: switch (protocol) {
1062: case CAIFPROTO_AT:
1063: sk->sk_priority = TC_PRIO_CONTROL;
1064: break;
1065: case CAIFPROTO_RFM:
1066: sk->sk_priority = TC_PRIO_INTERACTIVE_BULK;
1067: break;
1068: default:
1069: sk->sk_priority = TC_PRIO_BESTEFFORT;
1070: }
1071:
1072: /*
1073: * Lock in order to try to stop someone from opening the socket
1074: * too early.
1075: */
1076: lock_sock(&(cf_sk->sk));
1077:
1078: /* Initialize the nozero default sock structure data. */
1079: sock_init_data(sock, sk);
1080: sk->sk_destruct = caif_sock_destructor;
1081:
1082: mutex_init(&cf_sk->readlock); /* single task reading lock */
1083: cf_sk->layer.ctrlcmd = caif_ctrl_cb;
1084: cf_sk->sk.sk_socket->state = SS_UNCONNECTED;
1085: cf_sk->sk.sk_state = CAIF_DISCONNECTED;
1086:
1087: set_tx_flow_off(cf_sk);
1088: set_rx_flow_on(cf_sk);
1089:
1090: /* Set default options on configuration */
1091: cf_sk->conn_req.link_selector = CAIF_LINK_LOW_LATENCY;
1092: cf_sk->conn_req.protocol = protocol;
1093: release_sock(&cf_sk->sk);
1094: return 0;
1095: }
SourceFile:net/caif/caif_socket.c]
|
| 80/2 |
2026/05/23 09:51 |
llm |
expert |
0m
Model:
Tokens:
input: 77422
output: 23
thoughts: 660
Thoughts: **Analyzing the Privilege Requirements for the CAIF Vulnerability**
Okay, let's break this down systematically. My initial thought was that an unprivileged user wouldn't be able to even create `AF_CAIF` sockets, given the `caif_create` function's check for `CAP_SYS_ADMIN` or `CAP_NET_ADMIN`. But then, the `aoe` angle popped up, and it's always worth considering how broadcast packets on all interfaces can be exploited. Since `aoe` uses raw sockets or directly registers a handler, it *could* potentially be an attack vector. So, the question became: could an unprivileged user trigger `aoe` to send packets?
My instinct was to investigate the `aoe` driver. The reproducer seems to involve mounting `ocfs2`. However, I immediately recalled that `ocfs2` itself would likely require `CAP_SYS_ADMIN` to mount. Wait a minute, the reproducer uses `syz_mount_image`, which is a syzkaller pseudo-syscall that requires root. Okay, so the reproducer is definitely running with elevated privileges.
The primary concern is, how could an unprivileged user trigger the vulnerability? `aoe` does send discovery packets periodically or when a new interface comes up, but it's a block driver, so, is that even relevant? Then the key question is, *can* the bug be triggered by an unprivileged user?
The critical piece here is `caif_serial`, which needs to be attached to a tty. That attachment requires either `CAP_SYS_ADMIN` or `CAP_SYS_TTY_CONFIG`, which effectively eliminates unprivileged processes as a possible attack surface. We also know that since `capable()` is used, this also makes it inaccessible to user namespaces.
Alright, so the bug seems out of reach for unprivileged processes, I needed to confirm there are no alternative pathways to `handle_tx`.
I traced the `handle_tx` function back to `caif_xmit`, which is the `ndo_start_xmit` for the `caif` net_device. The `caif` net_device is, in turn, created within `ldisc_open` of `caif_serial.c`. Importantly, `ldisc_open` is called when `ioctl(fd, TIOCSETD, N_CAIF)` is called. And, I recall that this `ioctl` call *also* checks for `CAP_SYS_ADMIN` or `CAP_SYS_TTY_CONFIG`.
Therefore, that completely closes the loop. There is no way to create the `caif` net_device without those specific capabilities. This means the bug is strictly limited to privileged users. Just to be absolutely sure, I checked if there was another way to create a `caif` net_device through `caif_net_open`. Nope, it looks like `caif_serial.c` is the sole place that registers `caif` net_device with `caif_xmit`. Finally, I checked if any other drivers might be using `caif_xmit`. That appears to be it.
|
| 81/2 |
2026/05/23 09:51 |
tool |
codesearch-find-references |
0m
Args:
Results: map[References:<nil> TruncatedOutput:false]
|
| 82/2 |
2026/05/23 09:51 |
llm |
expert |
0m
Model:
Tokens:
input: 78796
output: 42
thoughts: 112
Thoughts: **Analyzing Potential Infinite Loop Bugs in Network Drivers**
Okay, so I'm digging into this infinite loop issue, and something just clicked. `caif_xmit` is *static* within `caif_serial.c`. That means it's only used within *that* specific file. That narrows down the scope considerably. Now, the question becomes, is this a pattern? Are there other drivers out there with a similar vulnerability?
Let's see... we've already checked a few: `ppp_async`, `n_hdlc`, `n_gsm`, `sixpack`, and `mkiss`. Nothing glaring there that I recall. Ah! Right, `slip`. `slip` has `sl_xmit`, which calls `sl_encaps`. Hmmm, `sl_encaps`. Now, *that* could be interesting. Let's get into `slip.c` and take a closer look at `sl_encaps`. This is where we might find a similar issue manifesting.
|
| 83/2 |
2026/05/23 09:51 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/slip/slip.c IncludeLines:true Name:sl_encaps]
Results: map[SourceCode: 375: /* Encapsulate one IP datagram and stuff into a TTY queue. */
376: static void sl_encaps(struct slip *sl, unsigned char *icp, int len)
377: {
378: unsigned char *p;
379: int actual, count;
380:
381: if (len > sl->mtu) { /* Sigh, shouldn't occur BUT ... */
382: printk(KERN_WARNING "%s: truncating oversized transmit packet!\n", sl->dev->name);
383: sl->dev->stats.tx_dropped++;
384: sl_unlock(sl);
385: return;
386: }
387:
388: p = icp;
389: #ifdef SL_INCLUDE_CSLIP
390: if (sl->mode & SL_MODE_CSLIP)
391: len = slhc_compress(sl->slcomp, p, len, sl->cbuff, &p, 1);
392: #endif
393: #ifdef CONFIG_SLIP_MODE_SLIP6
394: if (sl->mode & SL_MODE_SLIP6)
395: count = slip_esc6(p, sl->xbuff, len);
396: else
397: #endif
398: count = slip_esc(p, sl->xbuff, len);
399:
400: /* Order of next two lines is *very* important.
401: * When we are sending a little amount of data,
402: * the transfer may be completed inside the ops->write()
403: * routine, because it's running with interrupts enabled.
404: * In this case we *never* got WRITE_WAKEUP event,
405: * if we did not request it before write operation.
406: * 14 Oct 1994 Dmitry Gorodchanin.
407: */
408: set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
409: actual = sl->tty->ops->write(sl->tty, sl->xbuff, count);
410: #ifdef SL_CHECK_TRANSMIT
411: netif_trans_update(sl->dev);
412: #endif
413: sl->xleft = count - actual;
414: sl->xhead = sl->xbuff + actual;
415: #ifdef CONFIG_SLIP_SMART
416: /* VSV */
417: clear_bit(SLF_OUTWAIT, &sl->flags); /* reset outfill flag */
418: #endif
419: }
SourceFile:drivers/net/slip/slip.c]
|
| 84/2 |
2026/05/23 09:51 |
llm |
expert |
0m
Model:
Tokens:
input: 79958
output: 43
thoughts: 59
Thoughts: Here's my understanding of the `sl_encaps` function, keeping in mind my expertise:
**My Analysis of `sl_encaps`'s Write Operation**
Okay, so I'm looking at `sl_encaps`. It's pretty straightforward, it's just calling `write` once. No fancy looping or retries within that function itself. That's good, keeps it simple, less to debug.
Now, if that single `write` call returns a zero, which means something went wrong, the `actual` variable will also be zero. Consequently, `sl->xleft` will be set to the original `count`. Alright, that makes sense - essentially, it's indicating that no bytes were actually written. The full count of bytes that *should* have been written remains as pending in the write buffer.
The interesting part, then, is that `slip_write_wakeup` is invoked *later*. It's not happening immediately after the failed `write`. That suggests a delayed response, likely a mechanism to handle the write operation at a later, more appropriate time. I'd need to dig deeper into the system's interrupt or scheduler routines to understand when and how `slip_write_wakeup` is actually triggered, as well as the conditions that trigger it. My suspicion is, it's a callback designed to handle retries or signaling the availability of the transmit channel. I'll need to examine that function's implementation next.
|
| 85/2 |
2026/05/23 09:51 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/slip/slip.c IncludeLines:true Name:slip_write_wakeup]
Results: map[SourceCode: 450: /*
451: * Called by the driver when there's room for more data.
452: * Schedule the transmit.
453: */
454: static void slip_write_wakeup(struct tty_struct *tty)
455: {
456: struct slip *sl;
457:
458: rcu_read_lock();
459: sl = rcu_dereference(tty->disc_data);
460: if (sl)
461: schedule_work(&sl->tx_work);
462: rcu_read_unlock();
463: }
SourceFile:drivers/net/slip/slip.c]
|
| 86/2 |
2026/05/23 09:51 |
llm |
expert |
0m
Model:
Tokens:
input: 80587
output: 43
thoughts: 25
Thoughts: Okay, here's my interpretation of that thought process, from an expert's perspective:
**Diving into the Transmission Process**
Right, so `slip_write_wakeup` is the trigger, and it's responsible for scheduling a transmission task β that's `tx_work`. Excellent. My immediate next step is to examine what's actually happening within `sl_tx_work`. I need to understand the specifics of how this function is handling the transmission process. Are we talking about framing, buffering, hardware access, error handling, or some other aspects? I need to quickly assess its flow to understand how data is being prepped and sent. Let's delve in and see what's happening.
|
| 87/2 |
2026/05/23 09:52 |
tool |
codesearch-definition-source |
0m
Error:
Args: map[ContextFile:drivers/net/slip/slip.c IncludeLines:true Name:sl_tx_work]
Results: map[SourceCode: SourceFile:]
|
| 88/2 |
2026/05/23 09:52 |
llm |
expert |
0m
Model:
Tokens:
input: 80826
output: 21
thoughts: 16
Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience:
**Troubleshooting the Work Function**
Alright, time to dig in. My gut feeling is something's not quite right with the core work function. I need to zero in on that. Let's start with a sanity check β let's see, what's it called... right, `slip_transmit`. That's where the rubber meets the road, so to speak. If something's gumming up the works, `slip_transmit` (or whatever the actual function is) is the most likely culprit. I'll need to meticulously review the code there, looking for potential bottlenecks, race conditions, incorrect data handling, or anything that could be impacting throughput or introducing latency.
|
| 89/2 |
2026/05/23 09:52 |
tool |
grepper |
0m
Args: map[Expression:INIT_WORK.*tx_work]
Results: map[Output:drivers/bluetooth/btmtkuart.c=828=static int btmtkuart_probe(struct serdev_device *serdev)
--
drivers/bluetooth/btmtkuart.c-850-
drivers/bluetooth/btmtkuart.c:851: INIT_WORK(&bdev->tx_work, btmtkuart_tx_work);
drivers/bluetooth/btmtkuart.c-852- skb_queue_head_init(&bdev->txq);
--
drivers/bluetooth/btnxpuart.c=1815=static int nxp_serdev_probe(struct serdev_device *serdev)
--
drivers/bluetooth/btnxpuart.c-1832-
drivers/bluetooth/btnxpuart.c:1833: INIT_WORK(&nxpdev->tx_work, btnxpuart_tx_work);
drivers/bluetooth/btnxpuart.c-1834- skb_queue_head_init(&nxpdev->txq);
--
drivers/firmware/arm_scmi/transports/virtio.c=405=static int virtio_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
--
drivers/firmware/arm_scmi/transports/virtio.c-432-
drivers/firmware/arm_scmi/transports/virtio.c:433: INIT_WORK(&vioch->deferred_tx_work,
drivers/firmware/arm_scmi/transports/virtio.c-434- scmi_vio_deferred_tx_worker);
--
drivers/gpu/drm/display/drm_dp_mst_topology.c=5705=int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,
--
drivers/gpu/drm/display/drm_dp_mst_topology.c-5734- INIT_WORK(&mgr->work, drm_dp_mst_link_probe_work);
drivers/gpu/drm/display/drm_dp_mst_topology.c:5735: INIT_WORK(&mgr->tx_work, drm_dp_tx_work);
drivers/gpu/drm/display/drm_dp_mst_topology.c-5736- INIT_WORK(&mgr->delayed_destroy_work, drm_dp_delayed_destroy_work);
--
drivers/gpu/drm/panthor/panthor_mmu.c=2460=panthor_vm_bind_job_create(struct drm_file *file,
--
drivers/gpu/drm/panthor/panthor_mmu.c-2482-
drivers/gpu/drm/panthor/panthor_mmu.c:2483: INIT_WORK(&job->cleanup_op_ctx_work, panthor_vm_bind_job_cleanup_op_ctx_work);
drivers/gpu/drm/panthor/panthor_mmu.c-2484- kref_init(&job->refcount);
--
drivers/greybus/gb-beagleplay.c=412=static int hdlc_init(struct gb_beagleplay *bg)
drivers/greybus/gb-beagleplay.c-413-{
drivers/greybus/gb-beagleplay.c:414: INIT_WORK(&bg->tx_work, hdlc_transmit);
drivers/greybus/gb-beagleplay.c-415- spin_lock_init(&bg->tx_producer_lock);
--
drivers/hsi/controllers/omap_ssi_port.c=1108=static int ssi_port_probe(struct platform_device *pd)
--
drivers/hsi/controllers/omap_ssi_port.c-1162- INIT_DEFERRABLE_WORK(&omap_port->errqueue_work, ssi_process_errqueue);
drivers/hsi/controllers/omap_ssi_port.c:1163: INIT_WORK(&omap_port->work, start_tx_work);
drivers/hsi/controllers/omap_ssi_port.c-1164-
--
drivers/media/cec/usb/pulse8/pulse8-cec.c=835=static int pulse8_connect(struct serio *serio, struct serio_driver *drv)
--
drivers/media/cec/usb/pulse8/pulse8-cec.c-859- INIT_WORK(&pulse8->irq_work, pulse8_irq_work_handler);
drivers/media/cec/usb/pulse8/pulse8-cec.c:860: INIT_WORK(&pulse8->tx_work, pulse8_tx_work_handler);
drivers/media/cec/usb/pulse8/pulse8-cec.c-861- INIT_DELAYED_WORK(&pulse8->ping_eeprom_work,
--
drivers/media/pci/cx23885/cx23885-core.c=1967=static void cx23885_v4l2_dev_notify_init(struct cx23885_dev *dev)
--
drivers/media/pci/cx23885/cx23885-core.c-1970- INIT_WORK(&dev->ir_rx_work, cx23885_ir_rx_work_handler);
drivers/media/pci/cx23885/cx23885-core.c:1971: INIT_WORK(&dev->ir_tx_work, cx23885_ir_tx_work_handler);
drivers/media/pci/cx23885/cx23885-core.c-1972- dev->v4l2_dev.notify = cx23885_v4l2_dev_notify;
--
drivers/net/can/can327.c=1005=static int can327_ldisc_open(struct tty_struct *tty)
--
drivers/net/can/can327.c-1024- spin_lock_init(&elm->lock);
drivers/net/can/can327.c:1025: INIT_WORK(&elm->tx_work, can327_ldisc_tx_worker);
drivers/net/can/can327.c-1026-
--
drivers/net/can/m_can/m_can.c=2081=static int m_can_open(struct net_device *dev)
--
drivers/net/can/m_can/m_can.c-2120- cdev->tx_ops[i].cdev = cdev;
drivers/net/can/m_can/m_can.c:2121: INIT_WORK(&cdev->tx_ops[i].work, m_can_tx_work_queue);
drivers/net/can/m_can/m_can.c-2122- }
--
drivers/net/can/slcan/slcan-core.c=816=static int slcan_open(struct tty_struct *tty)
--
drivers/net/can/slcan/slcan-core.c-838- spin_lock_init(&sl->lock);
drivers/net/can/slcan/slcan-core.c:839: INIT_WORK(&sl->tx_work, slcan_transmit);
drivers/net/can/slcan/slcan-core.c-840- init_waitqueue_head(&sl->xcmd_wait);
--
drivers/net/can/spi/hi311x.c=826=static int hi3110_can_probe(struct spi_device *spi)
--
drivers/net/can/spi/hi311x.c-904- }
drivers/net/can/spi/hi311x.c:905: INIT_WORK(&priv->tx_work, hi3110_tx_work_handler);
drivers/net/can/spi/hi311x.c-906- INIT_WORK(&priv->restart_work, hi3110_restart_work_handler);
--
drivers/net/can/spi/mcp251x.c=1313=static int mcp251x_can_probe(struct spi_device *spi)
--
drivers/net/can/spi/mcp251x.c-1393- }
drivers/net/can/spi/mcp251x.c:1394: INIT_WORK(&priv->tx_work, mcp251x_tx_work_handler);
drivers/net/can/spi/mcp251x.c-1395- INIT_WORK(&priv->restart_work, mcp251x_restart_work_handler);
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c=1603=static int mcp251xfd_open(struct net_device *ndev)
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-1643- }
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c:1644: INIT_WORK(&priv->tx_work, mcp251xfd_tx_obj_write_sync);
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-1645-
--
drivers/net/can/usb/nct6694_canfd.c=721=static int nct6694_canfd_probe(struct platform_device *pdev)
--
drivers/net/can/usb/nct6694_canfd.c-761-
drivers/net/can/usb/nct6694_canfd.c:762: INIT_WORK(&priv->tx_work, nct6694_canfd_tx_work);
drivers/net/can/usb/nct6694_canfd.c-763-
--
drivers/net/ethernet/adi/adin1110.c=1566=static int adin1110_probe_netdevs(struct adin1110_priv *priv)
--
drivers/net/ethernet/adi/adin1110.c-1591- netdev->irq = priv->spidev->irq;
drivers/net/ethernet/adi/adin1110.c:1592: INIT_WORK(&port_priv->tx_work, adin1110_tx_work);
drivers/net/ethernet/adi/adin1110.c-1593- INIT_WORK(&port_priv->rx_mode_work, adin1110_rx_mode_work);
--
drivers/net/ethernet/davicom/dm9051.c=1164=static int dm9051_probe(struct spi_device *spi)
--
drivers/net/ethernet/davicom/dm9051.c-1190- INIT_WORK(&db->rxctrl_work, dm9051_rxctl_delay);
drivers/net/ethernet/davicom/dm9051.c:1191: INIT_WORK(&db->tx_work, dm9051_tx_delay);
drivers/net/ethernet/davicom/dm9051.c-1192-
--
drivers/net/ethernet/intel/igb/igb_ptp.c=1305=void igb_ptp_init(struct igb_adapter *adapter)
--
drivers/net/ethernet/intel/igb/igb_ptp.c-1391- spin_lock_init(&adapter->tmreg_lock);
drivers/net/ethernet/intel/igb/igb_ptp.c:1392: INIT_WORK(&adapter->ptp_tx_work, igb_ptp_tx_work);
drivers/net/ethernet/intel/igb/igb_ptp.c-1393-
--
drivers/net/ethernet/intel/ixgbe/ixgbe_ptp.c=1467=void ixgbe_ptp_init(struct ixgbe_adapter *adapter)
--
drivers/net/ethernet/intel/ixgbe/ixgbe_ptp.c-1479- /* we have a clock so we can initialize work now */
drivers/net/ethernet/intel/ixgbe/ixgbe_ptp.c:1480: INIT_WORK(&adapter->ptp_tx_work, ixgbe_ptp_tx_hwtstamp_work);
drivers/net/ethernet/intel/ixgbe/ixgbe_ptp.c-1481-
--
drivers/net/ethernet/marvell/prestera/prestera_rxtx.c=522=static int prestera_sdma_tx_init(struct prestera_sdma *sdma)
--
drivers/net/ethernet/marvell/prestera/prestera_rxtx.c-528-
drivers/net/ethernet/marvell/prestera/prestera_rxtx.c:529: INIT_WORK(&sdma->tx_work, prestera_sdma_tx_recycle_work_fn);
drivers/net/ethernet/marvell/prestera/prestera_rxtx.c-530- spin_lock_init(&sdma->tx_lock);
--
drivers/net/ethernet/micrel/ks8851_spi.c=403=static int ks8851_probe_spi(struct spi_device *spi)
--
drivers/net/ethernet/micrel/ks8851_spi.c-437- mutex_init(&kss->lock);
drivers/net/ethernet/micrel/ks8851_spi.c:438: INIT_WORK(&kss->tx_work, ks8851_tx_work);
drivers/net/ethernet/micrel/ks8851_spi.c-439-
--
drivers/net/ethernet/microchip/enc28j60.c=1524=static int enc28j60_probe(struct spi_device *spi)
--
drivers/net/ethernet/microchip/enc28j60.c-1543- mutex_init(&priv->lock);
drivers/net/ethernet/microchip/enc28j60.c:1544: INIT_WORK(&priv->tx_work, enc28j60_tx_work_handler);
drivers/net/ethernet/microchip/enc28j60.c-1545- INIT_WORK(&priv->setrx_work, enc28j60_setrx_work_handler);
--
drivers/net/ethernet/qualcomm/qca_uart.c=307=static int qca_uart_probe(struct serdev_device *serdev)
--
drivers/net/ethernet/qualcomm/qca_uart.c-330- spin_lock_init(&qca->lock);
drivers/net/ethernet/qualcomm/qca_uart.c:331: INIT_WORK(&qca->tx_work, qcauart_transmit);
drivers/net/ethernet/qualcomm/qca_uart.c-332-
--
drivers/net/ethernet/vertexcom/mse102x.c=690=static int mse102x_probe_spi(struct spi_device *spi)
--
drivers/net/ethernet/vertexcom/mse102x.c-732- mutex_init(&mses->lock);
drivers/net/ethernet/vertexcom/mse102x.c:733: INIT_WORK(&mses->tx_work, mse102x_tx_work);
drivers/net/ethernet/vertexcom/mse102x.c-734-
--
drivers/net/ethernet/wiznet/w5100.c=1077=int w5100_probe(struct device *dev, const struct w5100_ops *ops,
--
drivers/net/ethernet/wiznet/w5100.c-1152- INIT_WORK(&priv->rx_work, w5100_rx_work);
drivers/net/ethernet/wiznet/w5100.c:1153: INIT_WORK(&priv->tx_work, w5100_tx_work);
drivers/net/ethernet/wiznet/w5100.c-1154- INIT_WORK(&priv->setrx_work, w5100_setrx_work);
--
drivers/net/mctp/mctp-serial.c=440=static int mctp_serial_open(struct tty_struct *tty)
--
drivers/net/mctp/mctp-serial.c-471- spin_lock_init(&dev->lock);
drivers/net/mctp/mctp-serial.c:472: INIT_WORK(&dev->tx_work, mctp_serial_tx_work);
drivers/net/mctp/mctp-serial.c-473-
--
drivers/net/ovpn/socket.c=134=struct ovpn_socket *ovpn_socket_new(struct socket *sock, struct ovpn_peer *peer)
--
drivers/net/ovpn/socket.c-224- if (sk->sk_protocol == IPPROTO_TCP) {
drivers/net/ovpn/socket.c:225: INIT_WORK(&ovpn_sock->tcp_tx_work, ovpn_tcp_tx_work);
drivers/net/ovpn/socket.c-226- ovpn_sock->peer = peer;
--
drivers/net/slip/slip.c=739=static struct slip *sl_alloc(void)
--
drivers/net/slip/slip.c-766- spin_lock_init(&sl->lock);
drivers/net/slip/slip.c:767: INIT_WORK(&sl->tx_work, slip_transmit);
drivers/net/slip/slip.c-768- sl->mode = SL_MODE_DEFAULT;
--
drivers/net/wireguard/peer.c=21=struct wg_peer *wg_peer_create(struct wg_device *wg,
--
drivers/net/wireguard/peer.c-48- INIT_WORK(&peer->transmit_handshake_work, wg_packet_handshake_send_worker);
drivers/net/wireguard/peer.c:49: INIT_WORK(&peer->transmit_packet_work, wg_packet_tx_worker);
drivers/net/wireguard/peer.c-50- wg_prev_queue_init(&peer->tx_queue);
--
drivers/net/wireless/ath/ar5523/ar5523.c=1590=static int ar5523_probe(struct usb_interface *intf,
--
drivers/net/wireless/ath/ar5523/ar5523.c-1633- INIT_WORK(&ar->tx_wd_work, ar5523_tx_wd_work);
drivers/net/wireless/ath/ar5523/ar5523.c:1634: INIT_WORK(&ar->tx_work, ar5523_tx_work);
drivers/net/wireless/ath/ar5523/ar5523.c-1635- INIT_LIST_HEAD(&ar->tx_queue_pending);
--
drivers/net/wireless/ath/ath10k/core.c=3617=struct ath10k *ath10k_core_create(size_t priv_size, struct device *dev,
--
drivers/net/wireless/ath/ath10k/core.c-3721- init_completion(&ar->offchan_tx_completed);
drivers/net/wireless/ath/ath10k/core.c:3722: INIT_WORK(&ar->offchan_tx_work, ath10k_offchan_tx_work);
drivers/net/wireless/ath/ath10k/core.c-3723- skb_queue_head_init(&ar->offchan_tx_queue);
drivers/net/wireless/ath/ath10k/core.c-3724-
drivers/net/wireless/ath/ath10k/core.c:3725: INIT_WORK(&ar->wmi_mgmt_tx_work, ath10k_mgmt_over_wmi_tx_work);
drivers/net/wireless/ath/ath10k/core.c-3726- skb_queue_head_init(&ar->wmi_mgmt_tx_queue);
--
drivers/net/wireless/ath/ath10k/htc.c=914=int ath10k_htc_wait_target(struct ath10k_htc *htc)
--
drivers/net/wireless/ath/ath10k/htc.c-998-
drivers/net/wireless/ath/ath10k/htc.c:999: INIT_WORK(&ar->bundle_tx_work, ath10k_htc_bundle_tx_work);
drivers/net/wireless/ath/ath10k/htc.c-1000- INIT_WORK(&ar->tx_complete_work, ath10k_htc_tx_complete_work);
--
drivers/net/wireless/ath/ath11k/mac.c=7063=static int ath11k_mac_op_add_interface(struct ieee80211_hw *hw,
--
drivers/net/wireless/ath/ath11k/mac.c-7100- INIT_LIST_HEAD(&arvif->list);
drivers/net/wireless/ath/ath11k/mac.c:7101: INIT_WORK(&arvif->bcn_tx_work, ath11k_mac_bcn_tx_work);
drivers/net/wireless/ath/ath11k/mac.c-7102- INIT_DELAYED_WORK(&arvif->connection_loss_work,
--
drivers/net/wireless/ath/ath11k/mac.c=10746=int ath11k_mac_allocate(struct ath11k_base *ab)
--
drivers/net/wireless/ath/ath11k/mac.c-10804-
drivers/net/wireless/ath/ath11k/mac.c:10805: INIT_WORK(&ar->wmi_mgmt_tx_work, ath11k_mgmt_over_wmi_tx_work);
drivers/net/wireless/ath/ath11k/mac.c-10806- skb_queue_head_init(&ar->wmi_mgmt_tx_queue);
--
drivers/net/wireless/ath/ath9k/channel.c=1356=void ath9k_init_channel_context(struct ath_softc *sc)
drivers/net/wireless/ath/ath9k/channel.c-1357-{
drivers/net/wireless/ath/ath9k/channel.c:1358: INIT_WORK(&sc->chanctx_work, ath_chanctx_work);
drivers/net/wireless/ath/ath9k/channel.c-1359-
--
drivers/net/wireless/broadcom/b43/main.c=5563=static struct b43_wl *b43_wireless_init(struct b43_bus_dev *dev)
--
drivers/net/wireless/broadcom/b43/main.c-5606- INIT_WORK(&wl->txpower_adjust_work, b43_phy_txpower_adjust_work);
drivers/net/wireless/broadcom/b43/main.c:5607: INIT_WORK(&wl->tx_work, b43_tx_work);
drivers/net/wireless/broadcom/b43/main.c-5608-
--
drivers/net/wireless/broadcom/b43legacy/main.c=3789=static int b43legacy_wireless_init(struct ssb_device *dev)
--
drivers/net/wireless/broadcom/b43legacy/main.c-3832- INIT_WORK(&wl->beacon_update_trigger, b43legacy_beacon_update_trigger_work);
drivers/net/wireless/broadcom/b43legacy/main.c:3833: INIT_WORK(&wl->tx_work, b43legacy_tx_work);
drivers/net/wireless/broadcom/b43legacy/main.c-3834-
--
drivers/net/wireless/marvell/libertas_tf/main.c=555=struct lbtf_private *lbtf_add_card(void *card, struct device *dmdev,
--
drivers/net/wireless/marvell/libertas_tf/main.c-597- INIT_WORK(&priv->cmd_work, lbtf_cmd_work);
drivers/net/wireless/marvell/libertas_tf/main.c:598: INIT_WORK(&priv->tx_work, lbtf_tx_work);
drivers/net/wireless/marvell/libertas_tf/main.c-599-
--
drivers/net/wireless/quantenna/qtnfmac/core.c=393=static struct qtnf_wmac *qtnf_core_mac_alloc(struct qtnf_bus *bus,
--
drivers/net/wireless/quantenna/qtnfmac/core.c-432- qtnf_sta_list_init(&vif->sta_list);
drivers/net/wireless/quantenna/qtnfmac/core.c:433: INIT_WORK(&vif->high_pri_tx_work, qtnf_vif_send_data_high_pri);
drivers/net/wireless/quantenna/qtnfmac/core.c-434- skb_queue_head_init(&vif->high_pri_tx_queue);
--
drivers/net/wireless/realtek/rtw88/main.c=2109=int rtw_core_init(struct rtw_dev *rtwdev)
--
drivers/net/wireless/realtek/rtw88/main.c-2135- INIT_DELAYED_WORK(&coex->wl_ccklock_work, rtw_coex_wl_ccklock_work);
drivers/net/wireless/realtek/rtw88/main.c:2136: INIT_WORK(&rtwdev->tx_work, rtw_tx_work);
drivers/net/wireless/realtek/rtw88/main.c-2137- INIT_WORK(&rtwdev->c2h_work, rtw_c2h_work);
--
drivers/net/wireless/realtek/rtw88/usb.c=1012=static int rtw_usb_init_tx(struct rtw_dev *rtwdev)
--
drivers/net/wireless/realtek/rtw88/usb.c-1025-
drivers/net/wireless/realtek/rtw88/usb.c:1026: INIT_WORK(&rtwusb->tx_work, rtw_usb_tx_handler);
drivers/net/wireless/realtek/rtw88/usb.c-1027-
--
drivers/net/wireless/ti/wl1251/main.c=1582=struct ieee80211_hw *wl1251_alloc_hw(void)
--
drivers/net/wireless/ti/wl1251/main.c-1633- INIT_WORK(&wl->irq_work, wl1251_irq_work);
drivers/net/wireless/ti/wl1251/main.c:1634: INIT_WORK(&wl->tx_work, wl1251_tx_work);
drivers/net/wireless/ti/wl1251/main.c-1635-
--
drivers/net/wireless/ti/wlcore/main.c=6339=struct ieee80211_hw *wlcore_alloc_hw(size_t priv_size, u32 aggr_buf_size,
--
drivers/net/wireless/ti/wlcore/main.c-6379- INIT_WORK(&wl->netstack_work, wl1271_netstack_work);
drivers/net/wireless/ti/wlcore/main.c:6380: INIT_WORK(&wl->tx_work, wl1271_tx_work);
drivers/net/wireless/ti/wlcore/main.c-6381- INIT_WORK(&wl->recovery_work, wl1271_recovery_work);
--
drivers/net/wwan/t7xx/t7xx_hif_dpmaif_tx.c=605=int t7xx_dpmaif_txq_init(struct dpmaif_tx_queue *txq)
--
drivers/net/wwan/t7xx/t7xx_hif_dpmaif_tx.c-624-
drivers/net/wwan/t7xx/t7xx_hif_dpmaif_tx.c:625: INIT_WORK(&txq->dpmaif_tx_work, t7xx_dpmaif_tx_done);
drivers/net/wwan/t7xx/t7xx_hif_dpmaif_tx.c-626- spin_lock_init(&txq->tx_lock);
--
drivers/nfc/pn533/pn533.c=2738=struct pn533 *pn53x_common_init(u32 device_type,
--
drivers/nfc/pn533/pn533.c-2766- INIT_WORK(&priv->mi_rx_work, pn533_wq_mi_recv);
drivers/nfc/pn533/pn533.c:2767: INIT_WORK(&priv->mi_tx_work, pn533_wq_mi_send);
drivers/nfc/pn533/pn533.c-2768- INIT_WORK(&priv->tg_work, pn533_wq_tg_get_data);
drivers/nfc/pn533/pn533.c-2769- INIT_WORK(&priv->mi_tm_rx_work, pn533_wq_tm_mi_recv);
drivers/nfc/pn533/pn533.c:2770: INIT_WORK(&priv->mi_tm_tx_work, pn533_wq_tm_mi_send);
drivers/nfc/pn533/pn533.c-2771- INIT_DELAYED_WORK(&priv->poll_work, pn533_wq_poll);
--
drivers/nfc/st21nfca/dep.c=640=void st21nfca_dep_init(struct nfc_hci_dev *hdev)
--
drivers/nfc/st21nfca/dep.c-643-
drivers/nfc/st21nfca/dep.c:644: INIT_WORK(&info->dep_info.tx_work, st21nfca_tx_work);
drivers/nfc/st21nfca/dep.c-645- info->dep_info.curr_nfc_dep_pni = 0;
--
drivers/platform/surface/aggregator/ssh_request_layer.c=1025=int ssh_rtl_init(struct ssh_rtl *rtl, struct serdev_device *serdev,
--
drivers/platform/surface/aggregator/ssh_request_layer.c-1043-
drivers/platform/surface/aggregator/ssh_request_layer.c:1044: INIT_WORK(&rtl->tx.work, ssh_rtl_tx_work_fn);
drivers/platform/surface/aggregator/ssh_request_layer.c-1045-
--
drivers/staging/greybus/uart.c=804=static int gb_uart_probe(struct gbphy_device *gbphy_dev,
--
drivers/staging/greybus/uart.c-844-
drivers/staging/greybus/uart.c:845: INIT_WORK(&gb_tty->tx_work, gb_uart_tx_write_work);
drivers/staging/greybus/uart.c-846-
--
drivers/staging/nvec/nvec.c=777=static int tegra_nvec_probe(struct platform_device *pdev)
--
drivers/staging/nvec/nvec.c-839- INIT_WORK(&nvec->rx_work, nvec_dispatch);
drivers/staging/nvec/nvec.c:840: INIT_WORK(&nvec->tx_work, nvec_request_master);
drivers/staging/nvec/nvec.c-841-
--
drivers/tty/n_gsm.c=3276=static struct gsm_mux *gsm_alloc_mux(void)
--
drivers/tty/n_gsm.c-3300- timer_setup(&gsm->ka_timer, gsm_control_keep_alive, 0);
drivers/tty/n_gsm.c:3301: INIT_WORK(&gsm->tx_work, gsmld_write_task);
drivers/tty/n_gsm.c-3302- init_waitqueue_head(&gsm->event);
--
drivers/tty/serial/max310x.c=1267=static int max310x_probe(struct device *dev, const struct max310x_devtype *devtype,
--
drivers/tty/serial/max310x.c-1401- /* Initialize queue for start TX */
drivers/tty/serial/max310x.c:1402: INIT_WORK(&s->p[i].tx_work, max310x_tx_proc);
drivers/tty/serial/max310x.c-1403- /* Initialize queue for changing LOOPBACK mode */
--
drivers/tty/serial/sh-sci.c=1799=static void sci_request_dma(struct uart_port *port)
--
drivers/tty/serial/sh-sci.c-1841-
drivers/tty/serial/sh-sci.c:1842: INIT_WORK(&s->work_tx, sci_dma_tx_work_fn);
drivers/tty/serial/sh-sci.c-1843- s->chan_tx_saved = s->chan_tx = chan;
--
net/bluetooth/hci_core.c=2437=struct hci_dev *hci_alloc_dev_priv(int sizeof_priv)
--
net/bluetooth/hci_core.c-2548- INIT_WORK(&hdev->cmd_work, hci_cmd_work);
net/bluetooth/hci_core.c:2549: INIT_WORK(&hdev->tx_work, hci_tx_work);
net/bluetooth/hci_core.c-2550- INIT_WORK(&hdev->power_on, hci_power_on);
--
net/kcm/kcmsock.c=1184=static void init_kcm_sock(struct kcm_sock *kcm, struct kcm_mux *mux)
--
net/kcm/kcmsock.c-1213-
net/kcm/kcmsock.c:1214: INIT_WORK(&kcm->tx_work, kcm_tx_work);
net/kcm/kcmsock.c-1215- mutex_init(&kcm->tx_mutex);
--
net/mac802154/main.c=47=ieee802154_alloc_hw(size_t priv_data_len, const struct ieee802154_ops *ops)
--
net/mac802154/main.c-99-
net/mac802154/main.c:100: INIT_WORK(&local->sync_tx_work, ieee802154_xmit_sync_worker);
net/mac802154/main.c-101- INIT_DELAYED_WORK(&local->scan_work, mac802154_scan_worker);
--
net/nfc/hci/core.c=1010=int nfc_hci_register_device(struct nfc_hci_dev *hdev)
--
net/nfc/hci/core.c-1015-
net/nfc/hci/core.c:1016: INIT_WORK(&hdev->msg_tx_work, nfc_hci_msg_tx_work);
net/nfc/hci/core.c-1017-
--
net/nfc/llcp_core.c=1620=int nfc_llcp_register_device(struct nfc_dev *ndev)
--
net/nfc/llcp_core.c-1643- skb_queue_head_init(&local->tx_queue);
net/nfc/llcp_core.c:1644: INIT_WORK(&local->tx_work, nfc_llcp_tx_work);
net/nfc/llcp_core.c-1645-
--
net/nfc/nci/core.c=1235=int nci_register_device(struct nci_dev *ndev)
--
net/nfc/nci/core.c-1258-
net/nfc/nci/core.c:1259: INIT_WORK(&ndev->tx_work, nci_tx_work);
net/nfc/nci/core.c-1260- snprintf(name, sizeof(name), "%s_nci_tx_wq", dev_name(dev));
--
net/nfc/rawsock.c=323=static int rawsock_create(struct net *net, struct socket *sock,
--
net/nfc/rawsock.c-351- else {
net/nfc/rawsock.c:352: INIT_WORK(&nfc_rawsock(sk)->tx_work, rawsock_tx_work);
net/nfc/rawsock.c-353- nfc_rawsock(sk)->tx_work_scheduled = false;
--
net/vmw_vsock/virtio_transport.c=774=static int virtio_vsock_probe(struct virtio_device *vdev)
--
net/vmw_vsock/virtio_transport.c-804- INIT_WORK(&vsock->rx_work, virtio_transport_rx_work);
net/vmw_vsock/virtio_transport.c:805: INIT_WORK(&vsock->tx_work, virtio_transport_tx_work);
net/vmw_vsock/virtio_transport.c-806- INIT_WORK(&vsock->event_work, virtio_transport_event_work);
--
net/xfrm/espintcp.c=454=static int espintcp_init_sk(struct sock *sk)
--
net/xfrm/espintcp.c-500- rcu_assign_pointer(icsk->icsk_ulp_data, ctx);
net/xfrm/espintcp.c:501: INIT_WORK(&ctx->work, espintcp_tx_work);
net/xfrm/espintcp.c-502-
--
sound/drivers/serial-generic.c=321=static int snd_serial_generic_probe(struct serdev_device *serdev)
--
sound/drivers/serial-generic.c-344-
sound/drivers/serial-generic.c:345: INIT_WORK(&drvdata->tx_work, snd_serial_generic_tx_work);
sound/drivers/serial-generic.c-346-
]
|
| 90/2 |
2026/05/23 09:52 |
llm |
expert |
0m
Model:
Tokens:
input: 91164
output: 41
thoughts: 10
Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and presented as if it were my own internal monologue:
**Focusing In on the Core Function**
Alright, let's drill down. When I see `slip_transmit`, my mind immediately goes there β that's the *work function* in this context. Everything else, the surrounding code, the overall system design, is secondary right now. `slip_transmit` is the heart of the matter. It's the thing that *does* the actual transmitting, the core of the functionality we need to understand. Forget the fluff. That's the key variable. What is going on with that function? What are the parameters passed into that function? What are the return variables? Let's assume the function is doing what it is supposed to be doing, and dissect it from the inside out. What are the dependencies? The resource limitations? Let's see what is going on.
|
| 91/2 |
2026/05/23 09:52 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/slip/slip.c IncludeLines:true Name:slip_transmit]
Results: map[SourceCode: 421: /* Write out any remaining transmit buffer. Scheduled when tty is writable */
422: static void slip_transmit(struct work_struct *work)
423: {
424: struct slip *sl = container_of(work, struct slip, tx_work);
425: int actual;
426:
427: spin_lock_bh(&sl->lock);
428: /* First make sure we're connected. */
429: if (!sl->tty || sl->magic != SLIP_MAGIC || !netif_running(sl->dev)) {
430: spin_unlock_bh(&sl->lock);
431: return;
432: }
433:
434: if (sl->xleft <= 0) {
435: /* Now serial buffer is almost free & we can start
436: * transmission of another packet */
437: sl->dev->stats.tx_packets++;
438: clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
439: spin_unlock_bh(&sl->lock);
440: sl_unlock(sl);
441: return;
442: }
443:
444: actual = sl->tty->ops->write(sl->tty, sl->xhead, sl->xleft);
445: sl->xleft -= actual;
446: sl->xhead += actual;
447: spin_unlock_bh(&sl->lock);
448: }
SourceFile:drivers/net/slip/slip.c]
|
| 92/2 |
2026/05/23 09:52 |
llm |
expert |
0m
Model:
Tokens:
input: 91883
output: 66
thoughts: 2301
Thoughts: **Analysis of the CAIF Serial Infinite Loop Bug**
Okay, let's break this down. First, the core issue is an infinite loop in `handle_tx` within `caif_serial.c`. The root cause is a race condition where `tty_write_room` reports available space, but `tty->ops->write` immediately returns zero, leading to an unending loop. This specifically occurs after the serial port (UART) has been closed. During the close process, `uart_free_xmit_buf` is called which frees the buffers, but this happens *before* the network device is unregistered, creating a window.
Now, the crucial question is *how* to trigger this window. It's not in the simple `slip` code, but specifically in `caif_serial`, which requires either `CAP_SYS_ADMIN` or `CAP_SYS_TTY_CONFIG` to even open. So, an unprivileged process is immediately ruled out. The use of `capable()` confirms this isn't possible from a user namespace either.
Can we bypass the usual opening process somehow? Can sending a packet to the `caif` device itself trigger the bug? Yes, any write to the `caif` network device triggers `handle_tx`. But the `caif` device is created through `ldisc_open` which, you guessed it, requires those same capabilities. So a privileged user has to set things up.
But what if the device is already created and then closed? If root creates the device, and then closes the tty, then sends a packet, it will trigger the bug. If the device is up, any user can send a packet to it if they can route traffic to it. Can a regular user just create a socket and send packets? No, `AF_CAIF` sockets require `CAP_SYS_ADMIN` or `CAP_NET_ADMIN`. Raw sockets also require `CAP_NET_RAW` which means an unprivileged user cannot exploit it. IP packets are also not the answer because `caif` devices are not IP devices.
Aha! `aoe` broadcasts packets! Could this be a vector? The reproducer mounts `ocfs2`, but `mount` also requires root. So the reproducer *is* running as root, by way of `syz_mount_image`. The question then becomes, can an unprivileged user trigger `aoe`? Since `caif_serial` must be attached to the tty, and that attachment requires capabilities, an unprivileged user can't even get the setup right. So, no. The bug is inaccessible to unprivileged processes and user namespaces.
Therefore:
* **Exploitable: False** - It's a DoS, not a privilege escalation vulnerability.
* **DenialOfService: True** - The infinite loop causes an RCU stall.
* **Unprivileged: False** - Requires `CAP_SYS_ADMIN` or `CAP_SYS_TTY_CONFIG`.
* **UserNamespace: False** - `capable()` is used and only checks the initial user namespace.
* **VMGuestTrigger: False** - Not a KVM issue.
* **VMHostTrigger: False** - Not a KVM issue.
* **NetworkTrigger: False** - Triggered by local network transmission.
* **RemoteTrigger: False** - Not a remote attack vector.
* **PeripheralTrigger: False** - Not related to peripheral devices.
* **FilesystemTrigger: False** - Filesystem mount is just to trigger network packets, root cause is in `caif_serial`.
|
| 93/2 |
2026/05/23 09:52 |
tool |
set-results |
0m
Args: map[DenialOfService:true Exploitable:false FilesystemTrigger:false NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
Results: map[DenialOfService:true Exploitable:false FilesystemTrigger:false NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
|
| 94/2 |
2026/05/23 09:52 |
llm |
expert |
0m
Model:
Tokens:
input: 95094
output: 864
thoughts: 567
Thoughts: **My Analysis and Response**
Alright, the analysis is rock solid. I've walked through the code, confirmed the sequence of events, and I'm ready to craft the final response.
Let's break it down in my mind: This is a classic infinite loop bug within the `handle_tx` function, specifically in `drivers/net/caif/caif_serial.c`. It's a rather insidious one, stemming from the interaction between the `N_CAIF` line discipline attached to a serial TTY, and the timing of the TTY's closure.
The core of the problem lies in `uart_free_xmit_buf` during the TTY close process. It frees and reinitializes the transmit buffer (`xmit_buf`) and FIFO (`xmit_fifo`). The re-initialization of the FIFO is the key because `kfifo_avail`, and consequently `uart_write_room`, will then think there's space available. However, because `xmit_buf` is now `NULL`, `uart_write` will return 0, indicating a write failure.
The race condition comes into play because the `caif` network device can still be registered and up (though the TTY is closing). If a packet transmission occurs during this narrow window (think `aoe` discovery or `ocfs2` heartbeat traffic), `handle_tx` gets triggered. `handle_tx` sees that `tty_write_room` reports available space (1 byte), and dutifully calls `tty->ops->write`, which ends up being `uart_write`. `uart_write` fails, returning 0, yet the socket buffer (`skb`) isn't consumed. The subsequent loop in `handle_tx` repeats, repeatedly seeing a 1 from `tty_write_room`, a 0 from `uart_write`, and it enters an infinite loop. This infinite loop, happening with bottom halves disabled due to `ndo_start_xmit`, leads to an RCU stall and a soft lockup, resulting in a Denial of Service.
Regarding security, this is a pure DoS issue. There's no memory corruption or privilege escalation, which is good in a sense. The exploit is limited to the system halting due to RCU stalls, a Denial of Service. It's not exploitable for arbitrary code execution because there's no memory corruption, use-after-free, or out-of-bounds access. Furthermore, due to the requirements to attach `N_CAIF`, unprivileged users in user namespaces are not affected, which helps. It's solely triggered by internal network transmission during the specific race condition and not external network traffic.
|
| 95/1 |
2026/05/23 09:52 |
action |
format-explanation |
0m
Results: map[Explanation:**Bug Analysis:**
The bug is an infinite loop in `handle_tx()` within
`drivers/net/caif/caif_serial.c`, which leads to an RCU stall and soft lockup.
Here is the sequence of events that leads to the bug:
1. A privileged user opens a serial port (e.g., `/dev/ttyS3`) and attaches the
`N_CAIF` line discipline to it via `ioctl(TIOCSETD)`. This creates a `caif`
network device.
2. The user closes the serial port. During the TTY teardown process,
`tty_port_shutdown()` is called, which invokes `uart_free_xmit_buf()`.
3. `uart_free_xmit_buf()` frees the UART transmit buffer (`xmit_buf = NULL`) and
re-initializes the transmit FIFO (`INIT_KFIFO(port->xmit_fifo)`).
4. Because the FIFO is re-initialized (its mask is 0), `kfifo_avail()`
incorrectly returns `1`. Consequently, `uart_write_room()` also returns `1`.
5. There is a race window where the TTY's `xmit_buf` is freed, but the `caif`
network device is still registered and up (it is unregistered asynchronously via
a workqueue in `ser_release()`).
6. If a packet is transmitted over the `caif` network device during this window
(in the reproducer, this is triggered by `aoe` broadcasting discovery packets or
`ocfs2` heartbeat traffic), the network stack calls the device's
`ndo_start_xmit`, which maps to `caif_xmit()` and then `handle_tx()`.
7. `handle_tx()` checks `tty_write_room()`, which returns `1`. It then attempts
to write 1 byte using `tty->ops->write()` (which maps to `uart_write()`).
8. Because `xmit_buf` is `NULL`, `uart_write()` immediately returns `0`.
9. `handle_tx()` sees that `0` bytes were written, does not consume any data
from the `skb`, and loops again. It repeatedly gets `1` from `tty_write_room()`
and `0` from `uart_write()`, resulting in an infinite loop.
10. Since `ndo_start_xmit` is called with bottom halves disabled (or under a
spinlock), this infinite loop causes an RCU stall and soft lockup.
**Security Impact Assessment:**
* **Exploitable:** **False**. The bug is a pure infinite loop in the kernel
control flow. There is no memory corruption, use-after-free, or out-of-bounds
access involved. It cannot be exploited for privilege escalation or arbitrary
code execution.
* **Denial Of Service:** **True**. The infinite loop causes an RCU stall and
soft lockup, which hangs the CPU core and leads to a system crash or freeze.
* **Accessible From Unprivileged Processes:** **False**. Attaching the `N_CAIF`
line discipline requires `CAP_SYS_ADMIN` or `CAP_SYS_TTY_CONFIG` privileges.
This is explicitly checked in `ldisc_open()` in `caif_serial.c`. Unprivileged
users cannot set up the vulnerable state.
* **Accessible From User Namespaces:** **False**. The capability check in
`ldisc_open()` uses `capable()`, which checks for the capability in the initial
(global) user namespace. Therefore, even a root user inside a user namespace
cannot trigger this bug.
* **Network / Remote / Peripheral / Filesystem Trigger:** **False**. The bug is
triggered by local network transmission (TX path) during a specific race window
on a locally configured TTY. While the reproducer uses an `ocfs2` filesystem
mount, it is merely a side-effect to generate local network traffic (via `aoe`
or cluster heartbeats) and not a vulnerability in the filesystem parsing itself.]
|