| 0/0 |
2026/05/19 23:43 |
flow |
assessment-security |
34m
Results: map[DenialOfService:false Explanation:Based on the analysis of the stack traces and the source code, this is a
**benign data race** in the kernel's lockless printk ringbuffer. It has no
security impact.
### Root Cause Analysis
The KCSAN report highlights a data race between a writer (`vsnprintf`) and a
reader (`data_make_reusable`):
1. **Writer (CPU 1)**: A task is printing a network device log message
(`netdev_info` from `nsim_udp_tunnel_unset_port`). The printk subsystem
allocates a new block in the ringbuffer and uses `vsnprintf` to format the
string directly into this block's data section (`blk->data`).
2. **Reader (CPU 0)**: Another task is concurrently trying to allocate space in
the ringbuffer (triggered by an ext4 mount failure message). To free up space,
it calls `data_push_tail`, which iterates over old blocks via
`data_make_reusable`. It reads the block ID (`id = blk->id;`) of the oldest
block to check if it can be recycled.
Because the ringbuffer is a lockless circular buffer, newly allocated blocks
wrap around and overwrite old blocks. If CPU 0 reads the `id` of an old block
*after* CPU 1 has already pushed the tail and started writing its new string
over that exact memory location, CPU 0 will read bytes of the new string (e.g.,
the string `"type 2 "`) instead of a valid block ID.
This race is **intentional and safely handled** by the lockless algorithm. The
source code in `data_make_reusable` explicitly documents this exact scenario:
```c
/*
* Load the block ID from the data block. This is a data race
* against a writer that may have newly reserved this data
* area. If the loaded value matches a valid descriptor ID,
* the blk_lpos of that descriptor will be checked to make
* sure it points back to this data block. If the check fails,
* the data area has been recycled by another writer.
*/
id = blk->id; /* LMM(data_make_reusable:A) */
```
When `data_make_reusable` reads the garbage ID, it passes it to `desc_read()`.
The validation will fail (either the ID won't match the descriptor's state, or
the logical position won't match), causing it to safely abort, re-read the newly
updated tail position, and continue correctly.
### Security Impact
- **Exploitable / Memory Corruption**: **No**. `vsnprintf` is strictly bounded
by the allocated block size (`reserve_size`), so it cannot write out-of-bounds.
The reader safely discards the torn/garbage read.
- **Denial of Service**: **No**. The lockless algorithm handles the race
gracefully without crashing or hanging.
- **Triggerability**: While any unprivileged user can trigger concurrent
`printk` calls, the resulting data race is completely benign and does not affect
system stability or security. Exploitable:false FilesystemTrigger:false NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
|
| 1/1 |
2026/05/19 23:43 |
action |
syz-repro-to-c-repro |
0m
Results:
|
| 2/1 |
2026/05/19 23:43 |
action |
kernel-checkouter |
0m
Results: map[KernelSrc:/app/workdir/cache/src/de9834ab6d460d4437e3a407fa939fb9714dbc09]
|
| 3/1 |
2026/05/19 23:43 |
action |
kernel-builder |
14m
Results: map[KernelObj:/app/workdir/cache/build/efa47b8c6c6293928b028f478c2016d4b613867d]
|
| 4/1 |
2026/05/19 23:58 |
action |
codesearch-prepare |
11m
Results: map[Index:codesearch-index]
|
| 5/1 |
2026/05/20 00:10 |
agent |
expert |
7m
Model:
Results: map[DenialOfService:false 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).
Don't make assumptions; verify them with source code access. 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.
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:
EXT4-fs (loop4): too many log groups per flexible block group
==================================================================
BUG: KCSAN: data-race in data_push_tail / vsnprintf
write to 0xffffffff8936612c of 7 bytes by task 4294 on cpu 1:
vsnprintf+0x2ce/0x860 lib/vsprintf.c:2899
va_format lib/vsprintf.c:1723 [inline]
pointer+0x821/0xcb0 lib/vsprintf.c:2569
vsnprintf+0x491/0x860 lib/vsprintf.c:2952
vscnprintf+0x41/0x90 lib/vsprintf.c:3013
printk_sprint+0x30/0x2b0 kernel/printk/printk.c:2222
vprintk_store+0x57b/0x910 kernel/printk/printk.c:2364
vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
dev_vprintk_emit+0x242/0x2a0 drivers/base/core.c:4930
dev_printk_emit+0x84/0xb0 drivers/base/core.c:4941
__netdev_printk+0x34b/0x370 net/core/dev.c:12941
netdev_info+0xa6/0xd0 net/core/dev.c:12996
nsim_udp_tunnel_unset_port+0x190/0x1b0 drivers/net/netdevsim/udp_tunnels.c:59
udp_tunnel_nic_device_sync_one net/ipv4/udp_tunnel_nic.c:-1 [inline]
udp_tunnel_nic_device_sync_by_port net/ipv4/udp_tunnel_nic.c:249 [inline]
__udp_tunnel_nic_device_sync+0x575/0x9b0 net/ipv4/udp_tunnel_nic.c:292
udp_tunnel_nic_flush+0x21b/0x300 net/ipv4/udp_tunnel_nic.c:694
udp_tunnel_nic_unregister net/ipv4/udp_tunnel_nic.c:901 [inline]
udp_tunnel_nic_netdevice_event+0x8c0/0xd70 net/ipv4/udp_tunnel_nic.c:942
notifier_call_chain kernel/notifier.c:85 [inline]
raw_notifier_call_chain+0x72/0x1a0 kernel/notifier.c:453
call_netdevice_notifiers_info net/core/dev.c:2249 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
call_netdevice_notifiers net/core/dev.c:2301 [inline]
unregister_netdevice_many_notify+0xe2c/0x1650 net/core/dev.c:12421
unregister_netdevice_many net/core/dev.c:12484 [inline]
unregister_netdevice_queue+0x1cd/0x200 net/core/dev.c:12294
unregister_netdevice include/linux/netdevice.h:3444 [inline]
nsim_destroy+0x15b/0x5a0 drivers/net/netdevsim/netdev.c:1193
__nsim_dev_port_del+0xd2/0x140 drivers/net/netdevsim/dev.c:1547
nsim_dev_port_del_all drivers/net/netdevsim/dev.c:1561 [inline]
nsim_dev_reload_destroy+0x1a3/0x2c0 drivers/net/netdevsim/dev.c:1785
nsim_dev_reload_down+0x67/0x80 drivers/net/netdevsim/dev.c:1038
devlink_reload+0xad/0x590 net/devlink/dev.c:462
devlink_pernet_pre_exit+0xf9/0x260 net/devlink/core.c:558
ops_pre_exit_list net/core/net_namespace.c:161 [inline]
ops_undo_list+0xb5/0x420 net/core/net_namespace.c:234
cleanup_net+0x37c/0x5b0 net/core/net_namespace.c:702
process_one_work kernel/workqueue.c:3314 [inline]
process_scheduled_works+0x4f0/0x9c0 kernel/workqueue.c:3397
worker_thread+0x58a/0x780 kernel/workqueue.c:3478
kthread+0x22a/0x280 kernel/kthread.c:436
ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
read to 0xffffffff89366130 of 8 bytes by task 5879 on cpu 0:
data_make_reusable kernel/printk/printk_ringbuffer.c:608 [inline]
data_push_tail+0x100/0x470 kernel/printk/printk_ringbuffer.c:693
data_alloc+0x11b/0x390 kernel/printk/printk_ringbuffer.c:1089
prb_reserve+0x8d6/0xad0 kernel/printk/printk_ringbuffer.c:1727
vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
_printk+0x79/0xa0 kernel/printk/printk.c:2504
__ext4_msg+0x1aa/0x1c0 fs/ext4/super.c:1001
ext4_mb_init_backend fs/ext4/mballoc.c:3548 [inline]
ext4_mb_init+0xcea/0x11a0 fs/ext4/mballoc.c:3848
__ext4_fill_super fs/ext4/super.c:5654 [inline]
ext4_fill_super+0x3198/0x37c0 fs/ext4/super.c:5824
get_tree_bdev_flags+0x291/0x300 fs/super.c:1694
get_tree_bdev+0x1f/0x30 fs/super.c:1717
ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5856
vfs_get_tree+0x57/0x1d0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
do_new_mount_fc fs/namespace.c:3758 [inline]
do_new_mount+0x288/0x8d0 fs/namespace.c:3834
path_mount+0x4d0/0xbc0 fs/namespace.c:4154
do_mount fs/namespace.c:4167 [inline]
__do_sys_mount fs/namespace.c:4383 [inline]
__se_sys_mount+0x28c/0x2e0 fs/namespace.c:4360
__x64_sys_mount+0x67/0x80 fs/namespace.c:4360
x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
value changed: 0x3fffffffffffe00b -> 0x6d61662032206570
Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 5879 Comm: syz.4.457 Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================
EXT4-fs (loop4): failed to initialize mballoc (-12)
EXT4-fs (loop4): mount failed
Reply: Based on the analysis of the stack traces and the source code, this is a **benign data race** in the kernel's lockless printk ringbuffer. It has no security impact.
### Root Cause Analysis
The KCSAN report highlights a data race between a writer (`vsnprintf`) and a reader (`data_make_reusable`):
1. **Writer (CPU 1)**: A task is printing a network device log message (`netdev_info` from `nsim_udp_tunnel_unset_port`). The printk subsystem allocates a new block in the ringbuffer and uses `vsnprintf` to format the string directly into this block's data section (`blk->data`).
2. **Reader (CPU 0)**: Another task is concurrently trying to allocate space in the ringbuffer (triggered by an ext4 mount failure message). To free up space, it calls `data_push_tail`, which iterates over old blocks via `data_make_reusable`. It reads the block ID (`id = blk->id;`) of the oldest block to check if it can be recycled.
Because the ringbuffer is a lockless circular buffer, newly allocated blocks wrap around and overwrite old blocks. If CPU 0 reads the `id` of an old block *after* CPU 1 has already pushed the tail and started writing its new string over that exact memory location, CPU 0 will read bytes of the new string (e.g., the string `"type 2 "`) instead of a valid block ID.
This race is **intentional and safely handled** by the lockless algorithm. The source code in `data_make_reusable` explicitly documents this exact scenario:
```c
/*
* Load the block ID from the data block. This is a data race
* against a writer that may have newly reserved this data
* area. If the loaded value matches a valid descriptor ID,
* the blk_lpos of that descriptor will be checked to make
* sure it points back to this data block. If the check fails,
* the data area has been recycled by another writer.
*/
id = blk->id; /* LMM(data_make_reusable:A) */
```
When `data_make_reusable` reads the garbage ID, it passes it to `desc_read()`. The validation will fail (either the ID won't match the descriptor's state, or the logical position won't match), causing it to safely abort, re-read the newly updated tail position, and continue correctly.
### Security Impact
- **Exploitable / Memory Corruption**: **No**. `vsnprintf` is strictly bounded by the allocated block size (`reserve_size`), so it cannot write out-of-bounds. The reader safely discards the torn/garbage read.
- **Denial of Service**: **No**. The lockless algorithm handles the race gracefully without crashing or hanging.
- **Triggerability**: While any unprivileged user can trigger concurrent `printk` calls, the resulting data race is completely benign and does not affect system stability or security.
|
| 6/2 |
2026/05/20 00:10 |
llm |
expert |
0m
Model:
Tokens:
input: 6758
output: 53
thoughts: 1010
Thoughts: **Analyzing a KCSAN Data-Race in the Printk Subsystem**
Alright, a KCSAN data-race report has popped up. The report flags a race condition between `vsnprintf` and `data_push_tail` within the `printk` subsystem. Time to dig in and understand what's happening.
First, let's look at the stack traces. The write path shows `vsnprintf` at the top, which then calls down through `vprintk_store`, eventually making its way down to `nsim_udp_tunnel_unset_port`. The read path has `data_push_tail` as the suspect, called by `vprintk_store` and `vprintk_emit`. This looks like a classic producer-consumer scenario, with `vsnprintf` formatting the output and `data_push_tail` writing to the ring buffer. But why is it a data race?
Now for the details, I see `vsnprintf` is writing to `0xffffffff8936612c` and `data_push_tail` is reading from `0xffffffff89366130`. Given these addresses, I need to understand what's being accessed. Since they're kernel addresses, it's likely something in the kernel data/bss section, or perhaps a string literal. The value at that address changed, so let's look at the ASCII values. It changed from `0x3fffffffffffe00b` to `0x6d61662032206570`. Decoded, `0x6d61662032206570` gives "p e 2 f a m" or "pe 2 fam". The order doesn't quite make sense. If I reverse the bytes, I get "fam 2 ep". I think the print is "fam 2 ep".
Okay, now it's becoming clearer. `nsim_udp_tunnel_unset_port` is being called by the write stack trace. Let's examine the code within `nsim_udp_tunnel_unset_port`, it probably does a `printk` call. I suspect this `printk` call is formatting data for the ring buffer which is being read concurrently by `data_push_tail`, and this is where the race exists. The goal now is to see where the data is being written and to figure out where the read is occurring. I need to understand the relationship between these two seemingly disparate parts.
|
| 7/2 |
2026/05/20 00:10 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/netdevsim/udp_tunnels.c IncludeLines:true Name:nsim_udp_tunnel_unset_port]
Results: map[SourceCode: 37: static int
38: nsim_udp_tunnel_unset_port(struct net_device *dev, unsigned int table,
39: unsigned int entry, struct udp_tunnel_info *ti)
40: {
41: struct netdevsim *ns = netdev_priv(dev);
42: int ret;
43:
44: ret = -ns->udp_ports.inject_error;
45: ns->udp_ports.inject_error = 0;
46:
47: if (!ret) {
48: u32 val = be16_to_cpu(ti->port) << 16 | ti->type;
49:
50: if (val == ns->udp_ports.ports[table][entry]) {
51: ns->udp_ports.ports[table][entry] = 0;
52: } else {
53: WARN(1, "entry not installed %x vs %x\n",
54: val, ns->udp_ports.ports[table][entry]);
55: ret = -ENOENT;
56: }
57: }
58:
59: netdev_info(dev, "unset [%d, %d] type %d family %d port %d - %d\n",
60: table, entry, ti->type, ti->sa_family, ntohs(ti->port),
61: ret);
62: return ret;
63: }
SourceFile:drivers/net/netdevsim/udp_tunnels.c]
|
| 8/2 |
2026/05/20 00:10 |
llm |
expert |
0m
Model:
Tokens:
input: 8811
output: 40
thoughts: 243
Thoughts: **Deconstructing the `printk` Log Entry**
Okay, so I'm looking at this format string: `"family %d port %d - %d\n"`. Seems pretty standard, printing some family and port information, and maybe a range. I'm seeing "family" spelled out, and then I'm presented with a hex dump: `6d 61 66 20 32 20 65 70`. Let's break that down... `6d` is 'm', `61` is 'a', `66` is 'f', `20` is space, `32` is '2', `20` is space, and finally, `65` is 'e' and `70` is 'p'. Interesting, it appears the string I thought read "family" actually reads as "pe 2 fam".
Now, I'm trying to piece together how this is happening. There's some variable, `ti->type`, which is 2, and `ti->sa_family` that contains some value. "type 2 fam" becomes "pe 2 fam", so whatever is writing this, seems to be interpreting the data and flipping the "fam" and "pe".
So this must be related to the printk ring buffer. I wonder what is writing to the printk ringbuffer. I'm thinking about it, and `vsnprintf` is the usual suspect, isn't it? But, wait... `vsnprintf` itself writes to a *passed* buffer. Okay, so it's not writing directly to the printk ringbuffer, but it might be involved. Let's see... looking at the code... ah, yes! `vprintk_store` is the function that handles this, calling `printk_sprint` which, in turn, calls `vscnprintf`. Alright, so the puzzle pieces are starting to fit...
|
| 9/2 |
2026/05/20 00:10 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:kernel/printk/printk.c IncludeLines:true Name:vprintk_store]
Results: map[SourceCode:2268: __printf(4, 0)
2269: int vprintk_store(int facility, int level,
2270: const struct dev_printk_info *dev_info,
2271: const char *fmt, va_list args)
2272: {
2273: struct prb_reserved_entry e;
2274: enum printk_info_flags flags = 0;
2275: struct printk_record r;
2276: unsigned long irqflags;
2277: u16 trunc_msg_len = 0;
2278: char prefix_buf[8];
2279: u8 *recursion_ptr;
2280: u16 reserve_size;
2281: va_list args2;
2282: u32 caller_id;
2283: u16 text_len;
2284: int ret = 0;
2285: u64 ts_nsec;
2286:
2287: if (!printk_enter_irqsave(recursion_ptr, irqflags))
2288: return 0;
2289:
2290: /*
2291: * Since the duration of printk() can vary depending on the message
2292: * and state of the ringbuffer, grab the timestamp now so that it is
2293: * close to the call of printk(). This provides a more deterministic
2294: * timestamp with respect to the caller.
2295: */
2296: ts_nsec = local_clock();
2297:
2298: caller_id = printk_caller_id();
2299:
2300: /*
2301: * The sprintf needs to come first since the syslog prefix might be
2302: * passed in as a parameter. An extra byte must be reserved so that
2303: * later the vscnprintf() into the reserved buffer has room for the
2304: * terminating '\0', which is not counted by vsnprintf().
2305: */
2306: va_copy(args2, args);
2307: reserve_size = vsnprintf(&prefix_buf[0], sizeof(prefix_buf), fmt, args2) + 1;
2308: va_end(args2);
2309:
2310: if (reserve_size > PRINTKRB_RECORD_MAX)
2311: reserve_size = PRINTKRB_RECORD_MAX;
2312:
2313: /* Extract log level or control flags. */
2314: if (facility == 0)
2315: printk_parse_prefix(&prefix_buf[0], &level, &flags);
2316:
2317: if (level == LOGLEVEL_DEFAULT)
2318: level = default_message_loglevel;
2319:
2320: if (dev_info)
2321: flags |= LOG_NEWLINE;
2322:
2323: if (is_printk_force_console())
2324: flags |= LOG_FORCE_CON;
2325:
2326: if (flags & LOG_CONT) {
2327: prb_rec_init_wr(&r, reserve_size);
2328: if (prb_reserve_in_last(&e, prb, &r, caller_id, PRINTKRB_RECORD_MAX)) {
2329: text_len = printk_sprint(&r.text_buf[r.info->text_len], reserve_size,
2330: facility, &flags, fmt, args);
2331: r.info->text_len += text_len;
2332:
2333: if (flags & LOG_FORCE_CON)
2334: r.info->flags |= LOG_FORCE_CON;
2335:
2336: if (flags & LOG_NEWLINE) {
2337: r.info->flags |= LOG_NEWLINE;
2338: prb_final_commit(&e);
2339: } else {
2340: prb_commit(&e);
2341: }
2342:
2343: ret = text_len;
2344: goto out;
2345: }
2346: }
2347:
2348: /*
2349: * Explicitly initialize the record before every prb_reserve() call.
2350: * prb_reserve_in_last() and prb_reserve() purposely invalidate the
2351: * structure when they fail.
2352: */
2353: prb_rec_init_wr(&r, reserve_size);
2354: if (!prb_reserve(&e, prb, &r)) {
2355: /* truncate the message if it is too long for empty buffer */
2356: truncate_msg(&reserve_size, &trunc_msg_len);
2357:
2358: prb_rec_init_wr(&r, reserve_size + trunc_msg_len);
2359: if (!prb_reserve(&e, prb, &r))
2360: goto out;
2361: }
2362:
2363: /* fill message */
2364: text_len = printk_sprint(&r.text_buf[0], reserve_size, facility, &flags, fmt, args);
2365: if (trunc_msg_len)
2366: memcpy(&r.text_buf[text_len], trunc_msg, trunc_msg_len);
2367: r.info->text_len = text_len + trunc_msg_len;
2368: r.info->facility = facility;
2369: r.info->level = level & 7;
2370: r.info->flags = flags & 0x1f;
2371: r.info->ts_nsec = ts_nsec;
2372: r.info->caller_id = caller_id;
2373: if (dev_info)
2374: memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info));
2375: printk_store_execution_ctx(r.info);
2376:
2377: /* A message without a trailing newline can be continued. */
2378: if (!(flags & LOG_NEWLINE))
2379: prb_commit(&e);
2380: else
2381: prb_final_commit(&e);
2382:
2383: ret = text_len + trunc_msg_len;
2384: out:
2385: printk_exit_irqrestore(recursion_ptr, irqflags);
2386: return ret;
2387: }
SourceFile:kernel/printk/printk.c]
|
| 10/2 |
2026/05/20 00:10 |
llm |
expert |
0m
Model:
Tokens:
input: 11407
output: 45
thoughts: 224
Thoughts: **Analyzing a Potential Race Condition in the Kernel Logging Subsystem**
Okay, so I've traced this issue back through the kernel's logging infrastructure, and things are getting interesting. The write operation seems to originate in `vsnprintf`, specifically called from `printk_sprint`, which itself is called by `vprintk_store` β I'm looking at line 2364. My initial concern is that `vsnprintf` is writing to `r.text_buf[0]`.
But here's where it gets critical. The corresponding read happens in `data_make_reusable`. That's called from `data_push_tail`, which comes from `data_alloc`, and finally `prb_reserve`, which is *also* called by `vprintk_store` (but at line 2354). So I've got two operations, a write and a read, both stemming from `vprintk_store` but at different lines within that function.
The crucial observation now is that `prb_reserve` at line 2354 is associated with task 5879, which is running on CPU 0. Meanwhile, the `vprintk_store` call at line 2364 β the write β is being handled by task 4294, running on CPU 1.
So, to be absolutely clear: CPU 1 is *writing* to `r.text_buf`, which resides within the `printk` ring buffer. And CPU 0 is *reading* from that same memory location through `data_make_reusable`. This means I've got a potential race condition. The system could be attempting to read data that is not yet fully written, or being overwritten. Now I need to dive into `data_make_reusable` to see how it handles this potential problem.
|
| 11/2 |
2026/05/20 00:10 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:kernel/printk/printk_ringbuffer.c IncludeLines:true Name:data_make_reusable]
Results: map[SourceCode: 573: /*
574: * Given the text data ring, put the associated descriptor of each
575: * data block from @lpos_begin until @lpos_end into the reusable state.
576: *
577: * If there is any problem making the associated descriptor reusable, either
578: * the descriptor has not yet been finalized or another writer context has
579: * already pushed the tail lpos past the problematic data block. Regardless,
580: * on error the caller can re-load the tail lpos to determine the situation.
581: */
582: static bool data_make_reusable(struct printk_ringbuffer *rb,
583: unsigned long lpos_begin,
584: unsigned long lpos_end,
585: unsigned long *lpos_out)
586: {
587:
588: struct prb_data_ring *data_ring = &rb->text_data_ring;
589: struct prb_desc_ring *desc_ring = &rb->desc_ring;
590: struct prb_data_block *blk;
591: enum desc_state d_state;
592: struct prb_desc desc;
593: struct prb_data_blk_lpos *blk_lpos = &desc.text_blk_lpos;
594: unsigned long id;
595:
596: /* Loop until @lpos_begin has advanced to or beyond @lpos_end. */
597: while (need_more_space(data_ring, lpos_begin, lpos_end)) {
598: blk = to_block(data_ring, lpos_begin);
599:
600: /*
601: * Load the block ID from the data block. This is a data race
602: * against a writer that may have newly reserved this data
603: * area. If the loaded value matches a valid descriptor ID,
604: * the blk_lpos of that descriptor will be checked to make
605: * sure it points back to this data block. If the check fails,
606: * the data area has been recycled by another writer.
607: */
608: id = blk->id; /* LMM(data_make_reusable:A) */
609:
610: d_state = desc_read(desc_ring, id, &desc,
611: NULL, NULL); /* LMM(data_make_reusable:B) */
612:
613: switch (d_state) {
614: case desc_miss:
615: case desc_reserved:
616: case desc_committed:
617: return false;
618: case desc_finalized:
619: /*
620: * This data block is invalid if the descriptor
621: * does not point back to it.
622: */
623: if (blk_lpos->begin != lpos_begin)
624: return false;
625: desc_make_reusable(desc_ring, id);
626: break;
627: case desc_reusable:
628: /*
629: * This data block is invalid if the descriptor
630: * does not point back to it.
631: */
632: if (blk_lpos->begin != lpos_begin)
633: return false;
634: break;
635: }
636:
637: /* Advance @lpos_begin to the next data block. */
638: lpos_begin = blk_lpos->next;
639: }
640:
641: *lpos_out = lpos_begin;
642: return true;
643: }
SourceFile:kernel/printk/printk_ringbuffer.c]
|
| 12/2 |
2026/05/20 00:10 |
llm |
expert |
0m
Model:
Tokens:
input: 13203
output: 45
thoughts: 180
Thoughts: **Analyzing a Potential Data Race**
Okay, so the code comment is pretty clear: it's highlighting a potential data race. It's saying right up front that we're reading `blk->id` and that this read is susceptible to a writer that may be concurrently reserving this data area. That `/* LMM(data_make_reusable:A) */` tag seems important; I'll need to remember that. The comment explicitly states that the loaded `id` will then be validated against a descriptor ID, and if that validation fails, that this data area has been recycled by another writer. This is classic concurrency issue stuff.
Right, so `blk->id` is the key. Where is that in memory? Let's assume that `blk` is a pointer to the start of the `struct prb_data_block`. Okay, the code is reading `blk->id` - that is, an integer at the beginning of `struct prb_data_block`. Need to quickly review that struct definition to ensure I'm understanding the memory layout correctly.
|
| 13/2 |
2026/05/20 00:10 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:kernel/printk/printk_ringbuffer.c IncludeLines:true Name:prb_data_block]
Results: map[SourceCode: 341: /*
342: * A data block: mapped directly to the beginning of the data block area
343: * specified as a logical position within the data ring.
344: *
345: * @id: the ID of the associated descriptor
346: * @data: the writer data
347: *
348: * Note that the size of a data block is only known by its associated
349: * descriptor.
350: */
351: struct prb_data_block {
352: unsigned long id;
353: char data[];
354: };
SourceFile:kernel/printk/printk_ringbuffer.c]
|
| 14/2 |
2026/05/20 00:10 |
llm |
expert |
0m
Model:
Tokens:
input: 13870
output: 42
thoughts: 376
Thoughts: **Analyzing a Potential Memory Overlap**
Okay, let's break this down. First, `blk->id` is an 8-byte field. The critical part is seeing how this interacts with memory operations. Right now, I'm observing a write to address `0xffffffff8936612c` with a length of 7 bytes. Simultaneously, there's a read from `0xffffffff89366130`, also with a length of 8 bytes.
A quick calculation confirms that `0xffffffff8936612c` plus 4 bytes does indeed equal `0xffffffff89366130`. This is the crux of it. This means the write of 7 bytes is *partially* overlapping with the subsequent 8-byte read. That's immediately suspicious.
Now, I need to figure out *what* is writing and *what* is reading. I see `vsnprintf` is writing to `r.text_buf[0]`. Okay, `r.text_buf` points to `blk->data`. But wait, that's not quite right. `blk->data` is at an offset of either 8 (64-bit) or 4 (32-bit), right? The key question is this: if `vsnprintf` is writing to `blk->data`, then it *shouldn't* be touching `blk->id`.
Wait a second, let me recalculate where exactly the write is going. The write is from `0xffffffff8936612c` for 7 bytes, and the read is from `0xffffffff89366130` for 8 bytes. So, the write goes from `...2c` to `...32`, while the read goes from `...30` to `...37`. Therefore, they *do* overlap, and the overlap is at `...30`, `...31`, and `...32`.
So here's the core question: Why is `vsnprintf` *writing* into `blk->id`? Or, alternatively, why is the `data_make_reusable` *reading* `blk->data` *as* `blk->id`? Something is fundamentally misaligned here. I need to trace this back. The next step is to examine the `to_block` function.
|
| 15/2 |
2026/05/20 00:10 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:kernel/printk/printk_ringbuffer.c IncludeLines:true Name:to_block]
Results: map[SourceCode: 374: static struct prb_data_block *to_block(struct prb_data_ring *data_ring,
375: unsigned long begin_lpos)
376: {
377: return (void *)&data_ring->data[DATA_INDEX(data_ring, begin_lpos)];
378: }
SourceFile:kernel/printk/printk_ringbuffer.c]
|
| 16/2 |
2026/05/20 00:10 |
llm |
expert |
0m
Model:
Tokens:
input: 14938
output: 43
thoughts: 76
Thoughts: **Analyzing Potential Alignment Issues**
Okay, hold on a second. I'm looking at this `DATA_INDEX` calculation, and something's nagging at me. It's defined as `begin_lpos & (DATA_SIZE(data_ring) - 1)`. That's essentially a modular operation, extracting the index. But if `begin_lpos` isn't properly aligned β which I *assume* we're taking for granted here β then the function `to_block` could potentially return a pointer to memory that's also unaligned. That could lead to problems down the line, especially with certain data types or hardware architectures. The question becomes: is `begin_lpos` *guaranteed* to be aligned? I need to check the definition and usage of `prb_reserve`, as it seems most likely that `begin_lpos` is derived from that. I need to understand that logic precisely to be sure we aren't introducing undefined behavior. This needs immediate investigation.
|
| 17/2 |
2026/05/20 00:10 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:kernel/printk/printk_ringbuffer.c IncludeLines:true Name:prb_reserve]
Results: map[SourceCode:1632: /**
1633: * prb_reserve() - Reserve space in the ringbuffer.
1634: *
1635: * @e: The entry structure to setup.
1636: * @rb: The ringbuffer to reserve data in.
1637: * @r: The record structure to allocate buffers for.
1638: *
1639: * This is the public function available to writers to reserve data.
1640: *
1641: * The writer specifies the text size to reserve by setting the
1642: * @text_buf_size field of @r. To ensure proper initialization of @r,
1643: * prb_rec_init_wr() should be used.
1644: *
1645: * Context: Any context. Disables local interrupts on success.
1646: * Return: true if at least text data could be allocated, otherwise false.
1647: *
1648: * On success, the fields @info and @text_buf of @r will be set by this
1649: * function and should be filled in by the writer before committing. Also
1650: * on success, prb_record_text_space() can be used on @e to query the actual
1651: * space used for the text data block.
1652: *
1653: * Important: @info->text_len needs to be set correctly by the writer in
1654: * order for data to be readable and/or extended. Its value
1655: * is initialized to 0.
1656: */
1657: bool prb_reserve(struct prb_reserved_entry *e, struct printk_ringbuffer *rb,
1658: struct printk_record *r)
1659: {
1660: struct prb_desc_ring *desc_ring = &rb->desc_ring;
1661: struct printk_info *info;
1662: struct prb_desc *d;
1663: unsigned long id;
1664: u64 seq;
1665:
1666: if (!data_check_size(&rb->text_data_ring, r->text_buf_size))
1667: goto fail;
1668:
1669: /*
1670: * Descriptors in the reserved state act as blockers to all further
1671: * reservations once the desc_ring has fully wrapped. Disable
1672: * interrupts during the reserve/commit window in order to minimize
1673: * the likelihood of this happening.
1674: */
1675: local_irq_save(e->irqflags);
1676:
1677: if (!desc_reserve(rb, &id)) {
1678: /* Descriptor reservation failures are tracked. */
1679: atomic_long_inc(&rb->fail);
1680: local_irq_restore(e->irqflags);
1681: goto fail;
1682: }
1683:
1684: d = to_desc(desc_ring, id);
1685: info = to_info(desc_ring, id);
1686:
1687: /*
1688: * All @info fields (except @seq) are cleared and must be filled in
1689: * by the writer. Save @seq before clearing because it is used to
1690: * determine the new sequence number.
1691: */
1692: seq = info->seq;
1693: memset(info, 0, sizeof(*info));
1694:
1695: /*
1696: * Set the @e fields here so that prb_commit() can be used if
1697: * text data allocation fails.
1698: */
1699: e->rb = rb;
1700: e->id = id;
1701:
1702: /*
1703: * Initialize the sequence number if it has "never been set".
1704: * Otherwise just increment it by a full wrap.
1705: *
1706: * @seq is considered "never been set" if it has a value of 0,
1707: * _except_ for @infos[0], which was specially setup by the ringbuffer
1708: * initializer and therefore is always considered as set.
1709: *
1710: * See the "Bootstrap" comment block in printk_ringbuffer.h for
1711: * details about how the initializer bootstraps the descriptors.
1712: */
1713: if (seq == 0 && DESC_INDEX(desc_ring, id) != 0)
1714: info->seq = DESC_INDEX(desc_ring, id);
1715: else
1716: info->seq = seq + DESCS_COUNT(desc_ring);
1717:
1718: /*
1719: * New data is about to be reserved. Once that happens, previous
1720: * descriptors are no longer able to be extended. Finalize the
1721: * previous descriptor now so that it can be made available to
1722: * readers. (For seq==0 there is no previous descriptor.)
1723: */
1724: if (info->seq > 0)
1725: desc_make_final(rb, DESC_ID(id - 1));
1726:
1727: r->text_buf = data_alloc(rb, r->text_buf_size, &d->text_blk_lpos, id);
1728: /* If text data allocation fails, a data-less record is committed. */
1729: if (r->text_buf_size && !r->text_buf) {
1730: prb_commit(e);
1731: /* prb_commit() re-enabled interrupts. */
1732: goto fail;
1733: }
1734:
1735: r->info = info;
1736:
1737: /* Record full text space used by record. */
1738: e->text_space = space_used(&rb->text_data_ring, &d->text_blk_lpos);
1739:
1740: return true;
1741: fail:
1742: /* Make it clear to the caller that the reserve failed. */
1743: memset(r, 0, sizeof(*r));
1744: return false;
1745: }
SourceFile:kernel/printk/printk_ringbuffer.c]
|
| 18/2 |
2026/05/20 00:10 |
llm |
expert |
0m
Model:
Tokens:
input: 17087
output: 42
thoughts: 13
Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, and written as if they were my own immediate considerations:
**Allocating Memory and Returning Pointers**
Alright, so `data_alloc` is giving me back a pointer. That's the key. It's handing me the *address* of the memory it's just reserved. This is fundamental; it means I, as the calling code, am now responsible for managing that memory. I need to be *very* conscious of this. Am I getting back a plain pointer? Is it a typed pointer? What's the size of the allocation? Is there any associated metadata I need to be aware of (alignment, potential padding, etc.)? I need to know the allocation strategy being used internally and the associated implications to memory usage.
This pointer is essentially my handle to this newly allocated block. My primary concerns are around dereferencing and proper management. If I don't free it later, I have a leak. If I try to access memory outside the bounds of the allocation, I'm setting myself up for a crash or, worse, corrupting other data. This is all about safe and efficient memory manipulation. It all revolves around how I handle this returned pointer, and how I'm going to make sure that the memory that is pointed to is allocated correctly and freed up as well.
|
| 19/2 |
2026/05/20 00:10 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:kernel/printk/printk_ringbuffer.c IncludeLines:true Name:data_alloc]
Results: map[SourceCode:1048: /*
1049: * Allocate a new data block, invalidating the oldest data block(s)
1050: * if necessary. This function also associates the data block with
1051: * a specified descriptor.
1052: */
1053: static char *data_alloc(struct printk_ringbuffer *rb, unsigned int size,
1054: struct prb_data_blk_lpos *blk_lpos, unsigned long id)
1055: {
1056: struct prb_data_ring *data_ring = &rb->text_data_ring;
1057: struct prb_data_block *blk;
1058: unsigned long begin_lpos;
1059: unsigned long next_lpos;
1060:
1061: if (size == 0) {
1062: /*
1063: * Data blocks are not created for empty lines. Instead, the
1064: * reader will recognize these special lpos values and handle
1065: * it appropriately.
1066: */
1067: blk_lpos->begin = EMPTY_LINE_LPOS;
1068: blk_lpos->next = EMPTY_LINE_LPOS;
1069: return NULL;
1070: }
1071:
1072: size = to_blk_size(size);
1073:
1074: begin_lpos = atomic_long_read(&data_ring->head_lpos);
1075:
1076: do {
1077: next_lpos = get_next_lpos(data_ring, begin_lpos, size);
1078:
1079: /*
1080: * data_check_size() prevents data block allocation that could
1081: * cause illegal ringbuffer states. But double check that the
1082: * used space will not be bigger than the ring buffer. Wrapped
1083: * messages need to reserve more space, see get_next_lpos().
1084: *
1085: * Specify a data-less block when the check or the allocation
1086: * fails.
1087: */
1088: if (WARN_ON_ONCE(next_lpos - begin_lpos > DATA_SIZE(data_ring)) ||
1089: !data_push_tail(rb, next_lpos - DATA_SIZE(data_ring))) {
1090: blk_lpos->begin = FAILED_LPOS;
1091: blk_lpos->next = FAILED_LPOS;
1092: return NULL;
1093: }
1094:
1095: /*
1096: * 1. Guarantee any descriptor states that have transitioned
1097: * to reusable are stored before modifying the newly
1098: * allocated data area. A full memory barrier is needed
1099: * since other CPUs may have made the descriptor states
1100: * reusable. See data_push_tail:A about why the reusable
1101: * states are visible. This pairs with desc_read:D.
1102: *
1103: * 2. Guarantee any updated tail lpos is stored before
1104: * modifying the newly allocated data area. Another CPU may
1105: * be in data_make_reusable() and is reading a block ID
1106: * from this area. data_make_reusable() can handle reading
1107: * a garbage block ID value, but then it must be able to
1108: * load a new tail lpos. A full memory barrier is needed
1109: * since other CPUs may have updated the tail lpos. This
1110: * pairs with data_push_tail:B.
1111: */
1112: } while (!atomic_long_try_cmpxchg(&data_ring->head_lpos, &begin_lpos,
1113: next_lpos)); /* LMM(data_alloc:A) */
1114:
1115: blk = to_block(data_ring, begin_lpos);
1116: blk->id = id; /* LMM(data_alloc:B) */
1117:
1118: if (is_blk_wrapped(data_ring, begin_lpos, next_lpos)) {
1119: /* Wrapping data blocks store their data at the beginning. */
1120: blk = to_block(data_ring, 0);
1121:
1122: /*
1123: * Store the ID on the wrapped block for consistency.
1124: * The printk_ringbuffer does not actually use it.
1125: */
1126: blk->id = id;
1127: }
1128:
1129: blk_lpos->begin = begin_lpos;
1130: blk_lpos->next = next_lpos;
1131:
1132: return &blk->data[0];
1133: }
SourceFile:kernel/printk/printk_ringbuffer.c]
|
| 20/2 |
2026/05/20 00:10 |
llm |
expert |
0m
Model:
Tokens:
input: 18852
output: 40
thoughts: 273
Thoughts: **Debugging a Memory Overwrite**
Okay, so `data_alloc` is giving us the address of the start of the `data` buffer within our block (`blk`). Hang on, `blk->data` is supposed to be at offset 8, right? And `vsnprintf` is writing to `&blk->data[0]`. This should be at offset 8. The report, though, is showing writes to a very specific address, `0xffffffff8936612c`, for 7 bytes, and reads from `0xffffffff89366130` for 8 bytes. That's immediately suspicious.
Aha! `0xffffffff8936612c` plus 4 bytes is indeed `0xffffffff89366130`. Now, if the block's ID (`blk->id`) resides at address `0xffffffff89366130`, then the whole `blk` structure itself starts there, right? That would mean `blk->data` would be at `0xffffffff89366138`. But `vsnprintf` is *still* writing to `0xffffffff8936612c`! It's writing four bytes *before* where `blk` is supposed to reside! Something is definitely wrong.
Wait a minute... I remember a recent change... It's not `blk->data` that `vsnprintf` is writing to! It's actually writing to `prefix_buf`! Okay, time to go back to `vprintk_store` and see what's happening there.
|
| 21/2 |
2026/05/20 00:10 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:kernel/printk/printk.c IncludeLines:true Name:vprintk_store]
Results: map[SourceCode:2268: __printf(4, 0)
2269: int vprintk_store(int facility, int level,
2270: const struct dev_printk_info *dev_info,
2271: const char *fmt, va_list args)
2272: {
2273: struct prb_reserved_entry e;
2274: enum printk_info_flags flags = 0;
2275: struct printk_record r;
2276: unsigned long irqflags;
2277: u16 trunc_msg_len = 0;
2278: char prefix_buf[8];
2279: u8 *recursion_ptr;
2280: u16 reserve_size;
2281: va_list args2;
2282: u32 caller_id;
2283: u16 text_len;
2284: int ret = 0;
2285: u64 ts_nsec;
2286:
2287: if (!printk_enter_irqsave(recursion_ptr, irqflags))
2288: return 0;
2289:
2290: /*
2291: * Since the duration of printk() can vary depending on the message
2292: * and state of the ringbuffer, grab the timestamp now so that it is
2293: * close to the call of printk(). This provides a more deterministic
2294: * timestamp with respect to the caller.
2295: */
2296: ts_nsec = local_clock();
2297:
2298: caller_id = printk_caller_id();
2299:
2300: /*
2301: * The sprintf needs to come first since the syslog prefix might be
2302: * passed in as a parameter. An extra byte must be reserved so that
2303: * later the vscnprintf() into the reserved buffer has room for the
2304: * terminating '\0', which is not counted by vsnprintf().
2305: */
2306: va_copy(args2, args);
2307: reserve_size = vsnprintf(&prefix_buf[0], sizeof(prefix_buf), fmt, args2) + 1;
2308: va_end(args2);
2309:
2310: if (reserve_size > PRINTKRB_RECORD_MAX)
2311: reserve_size = PRINTKRB_RECORD_MAX;
2312:
2313: /* Extract log level or control flags. */
2314: if (facility == 0)
2315: printk_parse_prefix(&prefix_buf[0], &level, &flags);
2316:
2317: if (level == LOGLEVEL_DEFAULT)
2318: level = default_message_loglevel;
2319:
2320: if (dev_info)
2321: flags |= LOG_NEWLINE;
2322:
2323: if (is_printk_force_console())
2324: flags |= LOG_FORCE_CON;
2325:
2326: if (flags & LOG_CONT) {
2327: prb_rec_init_wr(&r, reserve_size);
2328: if (prb_reserve_in_last(&e, prb, &r, caller_id, PRINTKRB_RECORD_MAX)) {
2329: text_len = printk_sprint(&r.text_buf[r.info->text_len], reserve_size,
2330: facility, &flags, fmt, args);
2331: r.info->text_len += text_len;
2332:
2333: if (flags & LOG_FORCE_CON)
2334: r.info->flags |= LOG_FORCE_CON;
2335:
2336: if (flags & LOG_NEWLINE) {
2337: r.info->flags |= LOG_NEWLINE;
2338: prb_final_commit(&e);
2339: } else {
2340: prb_commit(&e);
2341: }
2342:
2343: ret = text_len;
2344: goto out;
2345: }
2346: }
2347:
2348: /*
2349: * Explicitly initialize the record before every prb_reserve() call.
2350: * prb_reserve_in_last() and prb_reserve() purposely invalidate the
2351: * structure when they fail.
2352: */
2353: prb_rec_init_wr(&r, reserve_size);
2354: if (!prb_reserve(&e, prb, &r)) {
2355: /* truncate the message if it is too long for empty buffer */
2356: truncate_msg(&reserve_size, &trunc_msg_len);
2357:
2358: prb_rec_init_wr(&r, reserve_size + trunc_msg_len);
2359: if (!prb_reserve(&e, prb, &r))
2360: goto out;
2361: }
2362:
2363: /* fill message */
2364: text_len = printk_sprint(&r.text_buf[0], reserve_size, facility, &flags, fmt, args);
2365: if (trunc_msg_len)
2366: memcpy(&r.text_buf[text_len], trunc_msg, trunc_msg_len);
2367: r.info->text_len = text_len + trunc_msg_len;
2368: r.info->facility = facility;
2369: r.info->level = level & 7;
2370: r.info->flags = flags & 0x1f;
2371: r.info->ts_nsec = ts_nsec;
2372: r.info->caller_id = caller_id;
2373: if (dev_info)
2374: memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info));
2375: printk_store_execution_ctx(r.info);
2376:
2377: /* A message without a trailing newline can be continued. */
2378: if (!(flags & LOG_NEWLINE))
2379: prb_commit(&e);
2380: else
2381: prb_final_commit(&e);
2382:
2383: ret = text_len + trunc_msg_len;
2384: out:
2385: printk_exit_irqrestore(recursion_ptr, irqflags);
2386: return ret;
2387: }
SourceFile:kernel/printk/printk.c]
|
| 22/2 |
2026/05/20 00:10 |
llm |
expert |
0m
Model:
Tokens:
input: 21416
output: 40
thoughts: 850
Thoughts: **A Deep Dive into a Potential Buffer Overwrite in `vprintk_store`**
Okay, let's break this down. I see that `vsnprintf` is called *twice* in `vprintk_store`. The first time, it calculates the size needed for a prefix, but the second time is where the problem seems to be. That second call to `vsnprintf` is within `printk_sprint`, which then calls `vscnprintf`, which *also* calls `vsnprintf`. That stack trace really drills it down.
The stack trace points to the second `vsnprintf` call, specifically within `printk_sprint`, as the culprit. I know that `vsnprintf` is writing to `r.text_buf[0]`. And, if I understand the memory layout correctly, that `r.text_buf` is actually just a pointer to `blk->data[0]`. Now, `blk->data` starts at offset 8 within the `blk` structure. So, if `vsnprintf` writes to `r.text_buf[0]`, it should be writing to `blk->data[0]`, right?
But then there's the memory addresses. I see a read occurring at `0xffffffff89366130`, and the write is at `0xffffffff8936612c`. Hold on a second... `0xffffffff8936612c` is *before* `0xffffffff89366130` by 4 bytes. If the read is to `blk->id` and the read happens at `0xffffffff89366130` then `blk->id` is at that location. But, if `blk->data` starts at offset 8 then `blk` is at `0xffffffff89366130` and `blk->data` is at `0xffffffff89366138`. So, why is `vsnprintf` writing at `0xffffffff8936612c`? That's the key question.
The write to `0xffffffff8936612c` consists of 7 bytes. So, `0xffffffff8936612c` plus 7 bytes goes up to `0xffffffff89366133`. And the read, it's 8 bytes, starts at `0xffffffff89366130`. So, this `vsnprintf` is writing to 4 bytes *before* `blk->id` and then overlapping into the first 3 bytes of `blk->id`.
The string being written is "pe 2 fam". Now, I'm thinking, could it be that `r.text_buf` isn't pointing where I think it is? Could it be pointing to `0xffffffff8936612c` directly? I need to check the code in `printk_sprint` and that function should make this clear. I'm going to look at the surrounding code for `r.text_buf` to check.
|
| 23/2 |
2026/05/20 00:11 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:kernel/printk/printk.c IncludeLines:true Name:printk_sprint]
Results: map[SourceCode:2215: __printf(5, 0)
2216: static u16 printk_sprint(char *text, u16 size, int facility,
2217: enum printk_info_flags *flags, const char *fmt,
2218: va_list args)
2219: {
2220: u16 text_len;
2221:
2222: text_len = vscnprintf(text, size, fmt, args);
2223:
2224: /* Mark and strip a trailing newline. */
2225: if (text_len && text[text_len - 1] == '\n') {
2226: text_len--;
2227: *flags |= LOG_NEWLINE;
2228: }
2229:
2230: /* Strip log level and control flags. */
2231: if (facility == 0) {
2232: u16 prefix_len;
2233:
2234: prefix_len = printk_parse_prefix(text, NULL, NULL);
2235: if (prefix_len) {
2236: text_len -= prefix_len;
2237: memmove(text, text + prefix_len, text_len);
2238: }
2239: }
2240:
2241: trace_console(text, text_len);
2242:
2243: return text_len;
2244: }
SourceFile:kernel/printk/printk.c]
|
| 24/2 |
2026/05/20 00:11 |
llm |
expert |
0m
Model:
Tokens:
input: 23437
output: 36
thoughts: 200
Thoughts: **Debugging a Potential Buffer Overflow**
Okay, so I'm digging into this code, and it looks like `vsnprintf` is writing to `text`. Hmm, I should clarify. `text` is actually referencing `r.text_buf[0]`. Wait a minute, what if the write isn't actually going *into* `r.text_buf`? Something's not right here. I need to look closer.
Let's check the stack trace: `vsnprintf`, then `va_format`, and then it looks like `pointer`, all in the `vsprintf.c` library. Ah! `va_format` is the key. The function call tree seems to indicate that `va_format` is the place to start looking.
My guess is that `pointer` is handling something like a `%pV` format specifier, or something similar. Maybe a modified `%p`? I can't quite remember if there are variations on that specifier.
Time to dive into `pointer` in `lib/vsprintf.c` and confirm my suspicion. Let's see what's going on in that part of the code.
|
| 25/2 |
2026/05/20 00:11 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:lib/vsprintf.c IncludeLines:true Name:pointer]
Results: map[SourceCode:2388: /*
2389: * Show a '%p' thing. A kernel extension is that the '%p' is followed
2390: * by an extra set of alphanumeric characters that are extended format
2391: * specifiers.
2392: *
2393: * Please update scripts/checkpatch.pl when adding/removing conversion
2394: * characters. (Search for "check for vsprintf extension").
2395: *
2396: * Right now we handle:
2397: *
2398: * - 'S' For symbolic direct pointers (or function descriptors) with offset
2399: * - 's' For symbolic direct pointers (or function descriptors) without offset
2400: * - '[Ss]R' as above with __builtin_extract_return_addr() translation
2401: * - 'S[R]b' as above with module build ID (for use in backtraces)
2402: * - '[Ff]' %pf and %pF were obsoleted and later removed in favor of
2403: * %ps and %pS. Be careful when re-using these specifiers.
2404: * - 'B' For backtraced symbolic direct pointers with offset
2405: * - 'Bb' as above with module build ID (for use in backtraces)
2406: * - 'R' For decoded struct resource, e.g., [mem 0x0-0x1f 64bit pref]
2407: * - 'r' For raw struct resource, e.g., [mem 0x0-0x1f flags 0x201]
2408: * - 'ra' For struct ranges, e.g., [range 0x0000000000000000 - 0x00000000000000ff]
2409: * - 'b[l]' For a bitmap, the number of bits is determined by the field
2410: * width which must be explicitly specified either as part of the
2411: * format string '%32b[l]' or through '%*b[l]', [l] selects
2412: * range-list format instead of hex format
2413: * - 'M' For a 6-byte MAC address, it prints the address in the
2414: * usual colon-separated hex notation
2415: * - 'm' For a 6-byte MAC address, it prints the hex address without colons
2416: * - 'MF' For a 6-byte MAC FDDI address, it prints the address
2417: * with a dash-separated hex notation
2418: * - '[mM]R' For a 6-byte MAC address, Reverse order (Bluetooth)
2419: * - 'I' [46] for IPv4/IPv6 addresses printed in the usual way
2420: * IPv4 uses dot-separated decimal without leading 0's (1.2.3.4)
2421: * IPv6 uses colon separated network-order 16 bit hex with leading 0's
2422: * [S][pfs]
2423: * Generic IPv4/IPv6 address (struct sockaddr *) that falls back to
2424: * [4] or [6] and is able to print port [p], flowinfo [f], scope [s]
2425: * - 'i' [46] for 'raw' IPv4/IPv6 addresses
2426: * IPv6 omits the colons (01020304...0f)
2427: * IPv4 uses dot-separated decimal with leading 0's (010.123.045.006)
2428: * [S][pfs]
2429: * Generic IPv4/IPv6 address (struct sockaddr *) that falls back to
2430: * [4] or [6] and is able to print port [p], flowinfo [f], scope [s]
2431: * - '[Ii][4S][hnbl]' IPv4 addresses in host, network, big or little endian order
2432: * - 'I[6S]c' for IPv6 addresses printed as specified by
2433: * https://tools.ietf.org/html/rfc5952
2434: * - 'E[achnops]' For an escaped buffer, where rules are defined by combination
2435: * of the following flags (see string_escape_mem() for the
2436: * details):
2437: * a - ESCAPE_ANY
2438: * c - ESCAPE_SPECIAL
2439: * h - ESCAPE_HEX
2440: * n - ESCAPE_NULL
2441: * o - ESCAPE_OCTAL
2442: * p - ESCAPE_NP
2443: * s - ESCAPE_SPACE
2444: * By default ESCAPE_ANY_NP is used.
2445: * - 'U' For a 16 byte UUID/GUID, it prints the UUID/GUID in the form
2446: * "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
2447: * Options for %pU are:
2448: * b big endian lower case hex (default)
2449: * B big endian UPPER case hex
2450: * l little endian lower case hex
2451: * L little endian UPPER case hex
2452: * big endian output byte order is:
2453: * [0][1][2][3]-[4][5]-[6][7]-[8][9]-[10][11][12][13][14][15]
2454: * little endian output byte order is:
2455: * [3][2][1][0]-[5][4]-[7][6]-[8][9]-[10][11][12][13][14][15]
2456: * - 'V' For a struct va_format which contains a format string * and va_list *,
2457: * call vsnprintf(->format, *->va_list).
2458: * Implements a "recursive vsnprintf".
2459: * Do not use this feature without some mechanism to verify the
2460: * correctness of the format string and va_list arguments.
2461: * - 'K' For a kernel pointer that should be hidden from unprivileged users.
2462: * Use only for procfs, sysfs and similar files, not printk(); please
2463: * read the documentation (path below) first.
2464: * - 'NF' For a netdev_features_t
2465: * - '4cc' V4L2 or DRM FourCC code, with endianness and raw numerical value.
2466: * - '4c[h[R]lb]' For generic FourCC code with raw numerical value. Both are
2467: * displayed in the big-endian format. This is the opposite of V4L2 or
2468: * DRM FourCCs.
2469: * The additional specifiers define what endianness is used to load
2470: * the stored bytes. The data might be interpreted using the host,
2471: * reversed host byte order, little-endian, or big-endian.
2472: * - 'h[CDN]' For a variable-length buffer, it prints it as a hex string with
2473: * a certain separator (' ' by default):
2474: * C colon
2475: * D dash
2476: * N no separator
2477: * The maximum supported length is 64 bytes of the input. Consider
2478: * to use print_hex_dump() for the larger input.
2479: * - 'a[pd]' For address types [p] phys_addr_t, [d] dma_addr_t and derivatives
2480: * (default assumed to be phys_addr_t, passed by reference)
2481: * - 'd[234]' For a dentry name (optionally 2-4 last components)
2482: * - 'D[234]' Same as 'd' but for a struct file
2483: * - 'g' For block_device name (gendisk + partition number)
2484: * - 't[RST][dt][r][s]' For time and date as represented by:
2485: * R struct rtc_time
2486: * S struct timespec64
2487: * T time64_t
2488: * - 'tSp' For time represented by struct timespec64 printed as <seconds>.<nanoseconds>
2489: * - 'C' For a clock, it prints the name (Common Clock Framework) or address
2490: * (legacy clock framework) of the clock
2491: * - 'G' For flags to be printed as a collection of symbolic strings that would
2492: * construct the specific value. Supported flags given by option:
2493: * p page flags (see struct page) given as pointer to unsigned long
2494: * g gfp flags (GFP_* and __GFP_*) given as pointer to gfp_t
2495: * v vma flags (VM_*) given as pointer to unsigned long
2496: * - 'OF[fnpPcCF]' For a device tree object
2497: * Without any optional arguments prints the full_name
2498: * f device node full_name
2499: * n device node name
2500: * p device node phandle
2501: * P device node path spec (name + @unit)
2502: * F device node flags
2503: * c major compatible string
2504: * C full compatible string
2505: * - 'fw[fP]' For a firmware node (struct fwnode_handle) pointer
2506: * Without an option prints the full name of the node
2507: * f full name
2508: * P node name, including a possible unit address
2509: * - 'x' For printing the address unmodified. Equivalent to "%lx".
2510: * Please read the documentation (path below) before using!
2511: * - '[ku]s' For a BPF/tracing related format specifier, e.g. used out of
2512: * bpf_trace_printk() where [ku] prefix specifies either kernel (k)
2513: * or user (u) memory to probe, and:
2514: * s a string, equivalent to "%s" on direct vsnprintf() use
2515: *
2516: * ** When making changes please also update:
2517: * Documentation/core-api/printk-formats.rst
2518: *
2519: * Note: The default behaviour (unadorned %p) is to hash the address,
2520: * rendering it useful as a unique identifier.
2521: *
2522: * There is also a '%pA' format specifier, but it is only intended to be used
2523: * from Rust code to format core::fmt::Arguments. Do *not* use it from C.
2524: * See rust/kernel/print.rs for details.
2525: */
2526: static noinline_for_stack
2527: char *pointer(const char *fmt, char *buf, char *end, void *ptr,
2528: struct printf_spec spec)
2529: {
2530: switch (*fmt) {
2531: case 'S':
2532: case 's':
2533: ptr = dereference_symbol_descriptor(ptr);
2534: fallthrough;
2535: case 'B':
2536: return symbol_string(buf, end, ptr, spec, fmt);
2537: case 'R':
2538: case 'r':
2539: return resource_or_range(fmt, buf, end, ptr, spec);
2540: case 'h':
2541: return hex_string(buf, end, ptr, spec, fmt);
2542: case 'b':
2543: switch (fmt[1]) {
2544: case 'l':
2545: return bitmap_list_string(buf, end, ptr, spec, fmt);
2546: default:
2547: return bitmap_string(buf, end, ptr, spec, fmt);
2548: }
2549: case 'M': /* Colon separated: 00:01:02:03:04:05 */
2550: case 'm': /* Contiguous: 000102030405 */
2551: /* [mM]F (FDDI) */
2552: /* [mM]R (Reverse order; Bluetooth) */
2553: return mac_address_string(buf, end, ptr, spec, fmt);
2554: case 'I': /* Formatted IP supported
2555: * 4: 1.2.3.4
2556: * 6: 0001:0203:...:0708
2557: * 6c: 1::708 or 1::1.2.3.4
2558: */
2559: case 'i': /* Contiguous:
2560: * 4: 001.002.003.004
2561: * 6: 000102...0f
2562: */
2563: return ip_addr_string(buf, end, ptr, spec, fmt);
2564: case 'E':
2565: return escaped_string(buf, end, ptr, spec, fmt);
2566: case 'U':
2567: return uuid_string(buf, end, ptr, spec, fmt);
2568: case 'V':
2569: return va_format(buf, end, ptr, spec);
2570: case 'K':
2571: return restricted_pointer(buf, end, ptr, spec);
2572: case 'N':
2573: return netdev_bits(buf, end, ptr, spec, fmt);
2574: case '4':
2575: return fourcc_string(buf, end, ptr, spec, fmt);
2576: case 'a':
2577: return address_val(buf, end, ptr, spec, fmt);
2578: case 'd':
2579: return dentry_name(buf, end, ptr, spec, fmt);
2580: case 't':
2581: return time_and_date(buf, end, ptr, spec, fmt);
2582: case 'C':
2583: return clock(buf, end, ptr, spec, fmt);
2584: case 'D':
2585: return file_dentry_name(buf, end, ptr, spec, fmt);
2586: #ifdef CONFIG_BLOCK
2587: case 'g':
2588: return bdev_name(buf, end, ptr, spec, fmt);
2589: #endif
2590:
2591: case 'G':
2592: return flags_string(buf, end, ptr, spec, fmt);
2593: case 'O':
2594: return device_node_string(buf, end, ptr, spec, fmt + 1);
2595: case 'f':
2596: return fwnode_string(buf, end, ptr, spec, fmt + 1);
2597: case 'A':
2598: if (!IS_ENABLED(CONFIG_RUST)) {
2599: WARN_ONCE(1, "Please remove %%pA from non-Rust code\n");
2600: return error_string(buf, end, "(%pA?)", spec);
2601: }
2602: return rust_fmt_argument(buf, end, ptr);
2603: case 'x':
2604: return pointer_string(buf, end, ptr, spec);
2605: case 'e':
2606: /* %pe with a non-ERR_PTR gets treated as plain %p */
2607: if (!IS_ERR(ptr))
2608: return default_pointer(buf, end, ptr, spec);
2609: return err_ptr(buf, end, ptr, spec);
2610: case 'u':
2611: case 'k':
2612: switch (fmt[1]) {
2613: case 's':
2614: return string(buf, end, ptr, spec);
2615: default:
2616: return error_string(buf, end, "(einval)", spec);
2617: }
2618: default:
2619: return default_pointer(buf, end, ptr, spec);
2620: }
2621: }
SourceFile:lib/vsprintf.c]
|
| 26/2 |
2026/05/20 00:11 |
llm |
expert |
0m
Model:
Tokens:
input: 28562
output: 42
thoughts: 61
Thoughts: **Investigating `va_format` and `%pV` in `dev_printk_emit`**
Okay, so I'm looking at this code and I see `va_format`, specifically this `case 'V'` handling. It's calling `va_format` to format something, presumably some kind of variable argument list. Hmm, interesting. Now, my brain immediately flags something, as `dev_printk_emit` uses `%pV`! I remember seeing that, and the connection is clear: `%pV` must be using this exact `va_format` function for its output. Let's delve into `dev_printk_emit` to confirm my suspicion and understand *exactly* how this interaction works. It seems a good idea to refresh my understanding and confirm it's as I recall.
|
| 27/2 |
2026/05/20 00:11 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/base/core.c IncludeLines:true Name:dev_vprintk_emit]
Results: map[SourceCode:4923: int dev_vprintk_emit(int level, const struct device *dev,
4924: const char *fmt, va_list args)
4925: {
4926: struct dev_printk_info dev_info;
4927:
4928: set_dev_info(dev, &dev_info);
4929:
4930: return vprintk_emit(0, level, &dev_info, fmt, args);
4931: }
SourceFile:drivers/base/core.c]
|
| 28/2 |
2026/05/20 00:11 |
llm |
expert |
0m
Model:
Tokens:
input: 28999
output: 41
thoughts: 51
Thoughts: Okay, let's see...
**Analyzing the Printing Mechanism**
Hmm, so `dev_vprintk_emit` essentially hands off the formatting job to `vprintk_emit`, using both the format string (`fmt`) and the arguments (`args`). Makes sense. But here's where my attention perks up: `__netdev_printk` uses `%pV`? That's not the usual `%s` or `%d` I'm used to seeing. This implies that the format string provided to `__netdev_printk` isn't directly passed to `vprintk_emit` via `fmt`, and must be going through some intermediary steps. Time to dive into the definition of `__netdev_printk` and understand how the `%pV` placeholder fits into the overall scheme. I need to figure out what's going on under the hood here.
|
| 29/2 |
2026/05/20 00:11 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:net/core/dev.c IncludeLines:true Name:__netdev_printk]
Results: map[SourceCode:12937: static void __netdev_printk(const char *level, const struct net_device *dev,
12938: struct va_format *vaf)
12939: {
12940: if (dev && dev->dev.parent) {
12941: dev_printk_emit(level[1] - '0',
12942: dev->dev.parent,
12943: "%s %s %s%s: %pV",
12944: dev_driver_string(dev->dev.parent),
12945: dev_name(dev->dev.parent),
12946: netdev_name(dev), netdev_reg_state(dev),
12947: vaf);
12948: } else if (dev) {
12949: printk("%s%s%s: %pV",
12950: level, netdev_name(dev), netdev_reg_state(dev), vaf);
12951: } else {
12952: printk("%s(NULL net_device): %pV", level, vaf);
12953: }
12954: }
SourceFile:net/core/dev.c]
|
| 30/2 |
2026/05/20 00:11 |
llm |
expert |
0m
Model:
Tokens:
input: 29624
output: 38
thoughts: 720
Thoughts: **Debugging a Kernel Printk Issue**
Okay, so I'm diving into this kernel printk issue. It looks like the `__netdev_printk` function uses `%pV`, which means `vsnprintf` is the one parsing it. And `vsnprintf` is calling `va_format`, which is calling `vsnprintf` recursively. The inner `vsnprintf` is formatting the actual message, specifically this one: "unset [%d, %d] type %d family %d port %d - %d\n".
But here's where it gets interesting. This inner `vsnprintf` is writing to `r.text_buf`, which from the looks of it is `&blk->data[0]`. So why am I seeing writes at a seemingly random address, `0xffffffff8936612c`? Is `r.text_buf` actually pointing there? If it is, then `blk->data` *must* be at that address too.
This means that `blk` would then be at `0xffffffff89366124`, assuming an 8-byte ID. However, I'm seeing a read at `0xffffffff89366130`. Wait, that's just `0xffffffff8936612c` plus 4. If `blk->data` is at `0xffffffff8936612c`, then `blk->id` would be at `0xffffffff89366124`. But the read is at `0xffffffff89366130` which looks suspect.
So, maybe `r.text_buf` isn't `blk->data`? Let's back up. I recall that `vprintk_store` has a local buffer named `prefix_buf[8]`, which is on the stack. Could that be it? But that address, `0xffffffff89...`, is a kernel address; it's likely in the data or BSS sections. That's a kernel text/data address. Could it be `trunc_msg`, the "<truncated>" message? No, that's read-only.
Aha! `vsnprintf` writes to the buffer it's given. So what buffer *is* passed to it in `vprintk_store`? Ah, `prefix_buf`! `reserve_size = vsnprintf(&prefix_buf[0], sizeof(prefix_buf), fmt, args2) + 1;` This is on the stack. But then `vprintk_store` also calls `text_len = printk_sprint(&r.text_buf[0], reserve_size, facility, &flags, fmt, args);`. `r.text_buf` is allocated by `data_alloc` and returned as `&blk->data[0]`.
`blk` comes from `to_block(data_ring, begin_lpos)`. So, is `data_ring->data` dynamically allocated, or static? For the main printk ringbuffer, I believe it's static. Time to double-check `prb`. Let's confirm that.
|
| 31/2 |
2026/05/20 00:11 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:kernel/printk/printk.c IncludeLines:true Name:prb]
Results: map[SourceCode: 524: struct printk_ringbuffer *prb = &printk_rb_static;
SourceFile:kernel/printk/printk.c]
|
| 32/2 |
2026/05/20 00:11 |
llm |
expert |
0m
Model:
Tokens:
input: 31134
output: 41
thoughts: 11
Thoughts: Okay, here's my attempt at summarizing that thought process, keeping in mind I'm speaking to a fellow expert:
**Investigating `printk_rb_static`**
Alright, time to dive in. My mind immediately goes to `printk_rb_static`. It's the logical starting point, isn't it? Let's assume we're dealing with something related to the static initialization or the behavior of a red-black tree (RB tree) implementation within the kernel's printk functionality. I want to understand exactly what's going on here, and whether there are any potential optimizations or, frankly, any issues that need addressing. So, `printk_rb_static` it is. Let's start digging!
|
| 33/2 |
2026/05/20 00:11 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:kernel/printk/printk.c IncludeLines:true Name:printk_rb_static]
Results: map[SourceCode: 519: _DEFINE_PRINTKRB(printk_rb_static, CONFIG_LOG_BUF_SHIFT - PRB_AVGBITS,
SourceFile:kernel/printk/printk.c]
|
| 34/2 |
2026/05/20 00:11 |
llm |
expert |
0m
Model:
Tokens:
input: 31407
output: 45
thoughts: 12
Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person:
**Initial Checkpoint: Examining `_DEFINE_PRINTKRB`**
Alright, my internal radar just pinged. First, I need to understand why I'm even thinking about `_DEFINE_PRINTKRB`. It's likely a debugging flag or perhaps a feature toggle related to Kerberos output. If I'm encountering a problem, and this has come to mind, then I'm probably suspecting an issue with Kerberos authentication or its associated debugging/logging output. The specific context will, of course, guide the next steps. Is it within a broader Kerberos implementation, a diagnostic utility, or something else entirely? Whatever the case, I need to quickly establish the potential impact of `_DEFINE_PRINTKRB` and if it is enabled. I need to be able to assess quickly what this flag controls and how it impacts the running system. What kind of output does it generate? Does it dump sensitive information? Could it be contributing to performance bottlenecks? Does it even exist? I'll need to figure out its current state and significance immediately. My next step will be to verify its definition and how it is used within the source code of the relevant codebase or the running system.
|
| 35/2 |
2026/05/20 00:11 |
tool |
codesearch-definition-source |
0m
Error: requested entity does not exist
Args: map[ContextFile:kernel/printk/printk_ringbuffer.h IncludeLines:true Name:_DEFINE_PRINTKRB]
Results: map[SourceCode: SourceFile:]
|
| 36/2 |
2026/05/20 00:11 |
llm |
expert |
0m
Model:
Tokens:
input: 31758
output: 20
thoughts: 13
Thoughts: Here's my summary, as though I'm thinking these thoughts:
**Grep Hunt for a Macro**
Okay, time to get to the heart of this. My initial instinct is to go straight for the jugular β let's see what we can find with `grep`. Specifically, I want to hunt down the macro `_DEFINE_PRINTKRB`. That should be a good starting point. This macro's definition is likely to tell me a lot about its purpose and usage. From there, I can probably determine what the surrounding context means. Iβm thinking, this will likely be a quick win that directs me towards the area that needs attention. Let's see what pops up.
|
| 37/2 |
2026/05/20 00:11 |
tool |
grepper |
0m
Args: map[Expression:_DEFINE_PRINTKRB]
Results: map[Output:kernel/printk/printk.c=507=static u32 log_buf_len = __LOG_BUF_LEN;
--
kernel/printk/printk.c-518-#endif
kernel/printk/printk.c:519:_DEFINE_PRINTKRB(printk_rb_static, CONFIG_LOG_BUF_SHIFT - PRB_AVGBITS,
kernel/printk/printk.c-520- PRB_AVGBITS, &__log_buf[0]);
--
kernel/printk/printk_ringbuffer.h=121=enum desc_state {
--
kernel/printk/printk_ringbuffer.h-254- */
kernel/printk/printk_ringbuffer.h:255:#define _DEFINE_PRINTKRB(name, descbits, avgtextbits, text_buf) \
kernel/printk/printk_ringbuffer.h-256-static struct prb_desc _##name##_descs[_DESCS_COUNT(descbits)] = { \
--
kernel/printk/printk_ringbuffer.h=277=static struct printk_ringbuffer name = { \
--
kernel/printk/printk_ringbuffer.h-302- * This is a macro for defining a ringbuffer and all internal structures
kernel/printk/printk_ringbuffer.h:303: * such that it is ready for immediate use. See _DEFINE_PRINTKRB() for a
kernel/printk/printk_ringbuffer.h-304- * variant where the text data buffer can be specified externally.
--
kernel/printk/printk_ringbuffer.h=307=static char _##name##_text[1U << ((avgtextbits) + (descbits))] \
kernel/printk/printk_ringbuffer.h-308- __aligned(__alignof__(unsigned long)); \
kernel/printk/printk_ringbuffer.h:309:_DEFINE_PRINTKRB(name, descbits, avgtextbits, &_##name##_text[0])
kernel/printk/printk_ringbuffer.h-310-
]
|
| 38/2 |
2026/05/20 00:12 |
llm |
expert |
0m
Model:
Tokens:
input: 32439
output: 40
thoughts: 24
Thoughts: Here's a summary of my immediate thought process, focusing on the provided context:
**Decoding the Log Buffer**
Okay, so I see `__log_buf`. My initial thought is, "Aha! That's the text buffer we're dealing with." That's the key variable to understand. The whole log is likely stored in that buffer. Given its name, it's highly likely it's a character array or similar.
Now the critical next step is to examine what's *in* `__log_buf`. I need to dive into its contents. Understanding the format of the information within this buffer will provide clues as to how to extract it, parse it, and use it. I'll need to check the code that writes to and reads from this variable to know how to interpret it.
|
| 39/2 |
2026/05/20 00:12 |
tool |
codesearch-definition-source |
0m
Error: requested entity does not exist
Args: map[ContextFile:kernel/printk/printk.c IncludeLines:true Name:__log_buf]
Results: map[SourceCode: SourceFile:]
|
| 40/2 |
2026/05/20 00:12 |
llm |
expert |
0m
Model:
Tokens:
input: 32697
output: 18
thoughts: 11
Thoughts: Here's my thought process, as requested:
**Grepping for `__log_buf`**
Okay, so I'm thinking about digging into this codebase, and the first thing that pops into my head is a quick and dirty way to find something interesting. Let's see... what's a likely candidate for a core logging buffer? My gut says `__log_buf`. It's a fairly common naming convention. Prefixing with double underscores often signifies something internal or implementation-specific, and `log_buf` pretty clearly points to a buffer related to logging. I want to quickly understand the logging architecture here, and pinpointing where the actual log data is held is a good starting point. This should give me a good handle on its architecture, its design. It's time to get hands on and see what I can find. So, time to fire up that `grep` command and see where this string lives within the source code. Let's see what we get!
|
| 41/2 |
2026/05/20 00:12 |
tool |
grepper |
0m
Args: map[Expression:__log_buf]
Results: map[Output:arch/microblaze/boot/Makefile=19=quiet_cmd_strip = STRIP $< $@$2
arch/microblaze/boot/Makefile:20: cmd_strip = $(STRIP) -K microblaze_start -K _end -K __log_buf \
arch/microblaze/boot/Makefile-21- -K _fdt_start $< -o $@$2
--
kernel/printk/printk.c=492=static struct latched_seq clear_seq = {
--
kernel/printk/printk.c-504-#define LOG_BUF_LEN_MAX ((u32)1 << 31)
kernel/printk/printk.c:505:static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
kernel/printk/printk.c:506:static char *log_buf = __log_buf;
kernel/printk/printk.c-507-static u32 log_buf_len = __LOG_BUF_LEN;
--
kernel/printk/printk.c=519=_DEFINE_PRINTKRB(printk_rb_static, CONFIG_LOG_BUF_SHIFT - PRB_AVGBITS,
kernel/printk/printk.c:520: PRB_AVGBITS, &__log_buf[0]);
kernel/printk/printk.c-521-
--
kernel/printk/printk.c=1149=void __init setup_log_buf(int early)
--
kernel/printk/printk.c-1171-
kernel/printk/printk.c:1172: if (log_buf != __log_buf)
kernel/printk/printk.c-1173- return;
--
tools/lib/bpf/libbpf.c=9807=int bpf_program__set_log_level(struct bpf_program *prog, __u32 log_level)
--
tools/lib/bpf/libbpf.c-9815-
tools/lib/bpf/libbpf.c:9816:const char *bpf_program__log_buf(const struct bpf_program *prog, size_t *log_size)
tools/lib/bpf/libbpf.c-9817-{
--
tools/lib/bpf/libbpf.h=1004=LIBBPF_API int bpf_program__set_log_level(struct bpf_program *prog, __u32 log_level);
tools/lib/bpf/libbpf.h:1005:LIBBPF_API const char *bpf_program__log_buf(const struct bpf_program *prog, size_t *log_size);
tools/lib/bpf/libbpf.h-1006-LIBBPF_API int bpf_program__set_log_buf(struct bpf_program *prog, char *log_buf, size_t log_size);
--
tools/lib/bpf/libbpf.map=315=LIBBPF_0.7.0 {
--
tools/lib/bpf/libbpf.map-318- bpf_program__expected_attach_type;
tools/lib/bpf/libbpf.map:319: bpf_program__log_buf;
tools/lib/bpf/libbpf.map-320- bpf_program__log_level;
]
|
| 42/2 |
2026/05/20 00:12 |
llm |
expert |
0m
Model:
Tokens:
input: 33779
output: 41
thoughts: 54
Thoughts: Okay, let's break this down.
**Initial Assessment of the Logging Buffer**
Right, so I'm looking at `__log_buf`, and initially, I'm thinking it's that static buffer defined in `kernel/printk/printk.c`. That's the first thing that jumps to mind, you know, the standard, fixed-size kind of approach. But hold on, something feels a little off. My gut is telling me there's more to it than just a static allocation. Wasn't there something about dynamic allocation? Time to double-check my assumptions and delve into `setup_log_buf`. Let's see what's really going on with this thing.
|
| 43/2 |
2026/05/20 00:12 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:kernel/printk/printk.c IncludeLines:true Name:setup_log_buf]
Results: map[SourceCode:1149: void __init setup_log_buf(int early)
1150: {
1151: struct printk_info *new_infos;
1152: unsigned int new_descs_count;
1153: struct prb_desc *new_descs;
1154: struct printk_info info;
1155: struct printk_record r;
1156: unsigned int text_size;
1157: size_t new_descs_size;
1158: size_t new_infos_size;
1159: unsigned long flags;
1160: char *new_log_buf;
1161: unsigned int free;
1162: u64 seq;
1163:
1164: /*
1165: * Some archs call setup_log_buf() multiple times - first is very
1166: * early, e.g. from setup_arch(), and second - when percpu_areas
1167: * are initialised.
1168: */
1169: if (!early)
1170: set_percpu_data_ready();
1171:
1172: if (log_buf != __log_buf)
1173: return;
1174:
1175: if (!early && !new_log_buf_len)
1176: log_buf_add_cpu();
1177:
1178: if (!new_log_buf_len) {
1179: /* Show the memory stats only once. */
1180: if (!early)
1181: goto out;
1182:
1183: return;
1184: }
1185:
1186: new_descs_count = new_log_buf_len >> PRB_AVGBITS;
1187: if (new_descs_count == 0) {
1188: pr_err("new_log_buf_len: %lu too small\n", new_log_buf_len);
1189: goto out;
1190: }
1191:
1192: new_log_buf = memblock_alloc(new_log_buf_len, LOG_ALIGN);
1193: if (unlikely(!new_log_buf)) {
1194: pr_err("log_buf_len: %lu text bytes not available\n",
1195: new_log_buf_len);
1196: goto out;
1197: }
1198:
1199: new_descs_size = new_descs_count * sizeof(struct prb_desc);
1200: new_descs = memblock_alloc(new_descs_size, LOG_ALIGN);
1201: if (unlikely(!new_descs)) {
1202: pr_err("log_buf_len: %zu desc bytes not available\n",
1203: new_descs_size);
1204: goto err_free_log_buf;
1205: }
1206:
1207: new_infos_size = new_descs_count * sizeof(struct printk_info);
1208: new_infos = memblock_alloc(new_infos_size, LOG_ALIGN);
1209: if (unlikely(!new_infos)) {
1210: pr_err("log_buf_len: %zu info bytes not available\n",
1211: new_infos_size);
1212: goto err_free_descs;
1213: }
1214:
1215: prb_rec_init_rd(&r, &info, &setup_text_buf[0], sizeof(setup_text_buf));
1216:
1217: prb_init(&printk_rb_dynamic,
1218: new_log_buf, ilog2(new_log_buf_len),
1219: new_descs, ilog2(new_descs_count),
1220: new_infos);
1221:
1222: local_irq_save(flags);
1223:
1224: log_buf_len = new_log_buf_len;
1225: log_buf = new_log_buf;
1226: new_log_buf_len = 0;
1227:
1228: free = __LOG_BUF_LEN;
1229: prb_for_each_record(0, &printk_rb_static, seq, &r) {
1230: text_size = add_to_rb(&printk_rb_dynamic, &r);
1231: if (text_size > free)
1232: free = 0;
1233: else
1234: free -= text_size;
1235: }
1236:
1237: prb = &printk_rb_dynamic;
1238:
1239: local_irq_restore(flags);
1240:
1241: /*
1242: * Copy any remaining messages that might have appeared from
1243: * NMI context after copying but before switching to the
1244: * dynamic buffer.
1245: */
1246: prb_for_each_record(seq, &printk_rb_static, seq, &r) {
1247: text_size = add_to_rb(&printk_rb_dynamic, &r);
1248: if (text_size > free)
1249: free = 0;
1250: else
1251: free -= text_size;
1252: }
1253:
1254: if (seq != prb_next_seq(&printk_rb_static)) {
1255: pr_err("dropped %llu messages\n",
1256: prb_next_seq(&printk_rb_static) - seq);
1257: }
1258:
1259: print_log_buf_usage_stats();
1260: pr_info("early log buf free: %u(%u%%)\n",
1261: free, (free * 100) / __LOG_BUF_LEN);
1262: return;
1263:
1264: err_free_descs:
1265: memblock_free(new_descs, new_descs_size);
1266: err_free_log_buf:
1267: memblock_free(new_log_buf, new_log_buf_len);
1268: out:
1269: print_log_buf_usage_stats();
1270: }
SourceFile:kernel/printk/printk.c]
|
| 44/2 |
2026/05/20 00:12 |
llm |
expert |
0m
Model:
Tokens:
input: 35906
output: 38
thoughts: 1091
Thoughts: **Analyzing a Kernel Data Write/Read Issue**
Okay, so I'm looking at this code and trying to figure out a potential memory corruption issue. It starts with a `log_buf` allocated with `memblock_alloc`, which I know returns a virtual address, not a physical one. The code mentions `0xffffffff8936612c` β that's a kernel data address. Wait, this address falls within the range of static kernel data. My first hunch is to check if `__log_buf` is actually located there.
If `__log_buf` is the active buffer, it's the static ring buffer. `setup_log_buf` is called early during boot, and if no new length is specified, it defaults to using `__log_buf`. So, seems likely that `__log_buf` is in play.
Now, here's where it gets interesting. `vsnprintf` appears to be writing to `r.text_buf[0]`, and `r.text_buf` is aliased to `&blk->data[0]`. This makes `blk->data` start at `0xffffffff8936612c`. However, `blk->data` is at an offset of 8 bytes from `blk`. So, `blk` itself must start at `0xffffffff89366124`. This would make `blk->id` at `0xffffffff89366124`.
But, wait! There's a read occurring at `0xffffffff89366130`. I have to understand why the read and write addresses are different. I'll check the `to_block` function.
```c
static struct prb_data_block *to_block(struct prb_data_ring *data_ring,
unsigned long begin_lpos)
{
return (void *)&data_ring->data[DATA_INDEX(data_ring, begin_lpos)];
}
```
The `DATA_INDEX` is calculated as `begin_lpos & (DATA_SIZE(data_ring) - 1)`. So, `begin_lpos` seems to be an offset within the ring buffer. If `begin_lpos` is, say, `0x12c`, `to_block` returns `&data_ring->data[0x12c]`. This means `blk->id` would be at `0x12c` and `blk->data` would be at `0x134`.
However, `vsnprintf` is writing to `0xffffffff8936612c`, and it's reading at `0xffffffff89366130`. This means `vsnprintf` is writing 4 bytes *before* `blk->id`, which is a red flag. The write is 7 bytes. The read is 8 bytes.
`vsnprintf` is writing from address `...2c` to `...32` which is the string. `...30` to `...37` is the read. Why is it writing before the read?
I know the write is "pe 2 fam".
Given that `vsnprintf` writes a formatted string, I have to check the format string itself. The format string is `"%s %s %s%s: %pV"`, which leads me to `__netdev_printk`:
```c
dev_printk_emit(level[1] - '0',
dev->dev.parent,
"%s %s %s%s: %pV",
dev_driver_string(dev->dev.parent),
dev_name(dev->dev.parent),
netdev_name(dev), netdev_reg_state(dev),
vaf);
```
The output of `__netdev_printk` is: `"netdevsim netdevsim0 netdevsim0: unset [0, 0] type 2 family 2 port 0 - 0\n"`.
The substring "type 2 family" corresponds to what is written. "pe 2 fam" is from "type 2 family". "type 2 fam" is 10 bytes and the write is 7 bytes! Why is `vsnprintf` writing 7 bytes, it has the data for 10? Maybe `vsnprintf` writes in chunks? I'll have to investigate `vsnprintf`'s implementation in `lib/vsprintf.c` to see how it handles output and truncation.
|
| 45/2 |
2026/05/20 00:12 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:lib/vsprintf.c IncludeLines:true Name:vsnprintf]
Results: map[SourceCode:2836: /**
2837: * vsnprintf - Format a string and place it in a buffer
2838: * @buf: The buffer to place the result into
2839: * @size: The size of the buffer, including the trailing null space
2840: * @fmt_str: The format string to use
2841: * @args: Arguments for the format string
2842: *
2843: * This function generally follows C99 vsnprintf, but has some
2844: * extensions and a few limitations:
2845: *
2846: * - ``%n`` is unsupported
2847: * - ``%p*`` is handled by pointer()
2848: *
2849: * See pointer() or Documentation/core-api/printk-formats.rst for more
2850: * extensive description.
2851: *
2852: * **Please update the documentation in both places when making changes**
2853: *
2854: * The return value is the number of characters which would
2855: * be generated for the given input, excluding the trailing
2856: * '\0', as per ISO C99. If you want to have the exact
2857: * number of characters written into @buf as return value
2858: * (not including the trailing '\0'), use vscnprintf(). If the
2859: * return is greater than or equal to @size, the resulting
2860: * string is truncated.
2861: *
2862: * If you're not already dealing with a va_list consider using snprintf().
2863: */
2864: int vsnprintf(char *buf, size_t size, const char *fmt_str, va_list args)
2865: {
2866: char *str, *end;
2867: struct printf_spec spec = {0};
2868: struct fmt fmt = {
2869: .str = fmt_str,
2870: .state = FORMAT_STATE_NONE,
2871: };
2872:
2873: /* Reject out-of-range values early. Large positive sizes are
2874: used for unknown buffer sizes. */
2875: if (WARN_ON_ONCE(size > INT_MAX))
2876: return 0;
2877:
2878: str = buf;
2879: end = buf + size;
2880:
2881: /* Make sure end is always >= buf */
2882: if (end < buf) {
2883: end = ((void *)-1);
2884: size = end - buf;
2885: }
2886:
2887: while (*fmt.str) {
2888: const char *old_fmt = fmt.str;
2889:
2890: fmt = format_decode(fmt, &spec);
2891:
2892: switch (fmt.state) {
2893: case FORMAT_STATE_NONE: {
2894: int read = fmt.str - old_fmt;
2895: if (str < end) {
2896: int copy = read;
2897: if (copy > end - str)
2898: copy = end - str;
2899: memcpy(str, old_fmt, copy);
2900: }
2901: str += read;
2902: continue;
2903: }
2904:
2905: case FORMAT_STATE_NUM: {
2906: unsigned long long num;
2907:
2908: if (fmt.size > sizeof(int))
2909: num = va_arg(args, long long);
2910: else
2911: num = convert_num_spec(va_arg(args, int), fmt.size, spec);
2912: str = number(str, end, num, spec);
2913: continue;
2914: }
2915:
2916: case FORMAT_STATE_WIDTH:
2917: set_field_width(&spec, va_arg(args, int));
2918: continue;
2919:
2920: case FORMAT_STATE_PRECISION:
2921: set_precision(&spec, va_arg(args, int));
2922: continue;
2923:
2924: case FORMAT_STATE_CHAR: {
2925: char c;
2926:
2927: if (!(spec.flags & LEFT)) {
2928: while (--spec.field_width > 0) {
2929: if (str < end)
2930: *str = ' ';
2931: ++str;
2932:
2933: }
2934: }
2935: c = (unsigned char) va_arg(args, int);
2936: if (str < end)
2937: *str = c;
2938: ++str;
2939: while (--spec.field_width > 0) {
2940: if (str < end)
2941: *str = ' ';
2942: ++str;
2943: }
2944: continue;
2945: }
2946:
2947: case FORMAT_STATE_STR:
2948: str = string(str, end, va_arg(args, char *), spec);
2949: continue;
2950:
2951: case FORMAT_STATE_PTR:
2952: str = pointer(fmt.str, str, end, va_arg(args, void *),
2953: spec);
2954: while (isalnum(*fmt.str))
2955: fmt.str++;
2956: continue;
2957:
2958: case FORMAT_STATE_PERCENT_CHAR:
2959: if (str < end)
2960: *str = '%';
2961: ++str;
2962: continue;
2963:
2964: default:
2965: /*
2966: * Presumably the arguments passed gcc's type
2967: * checking, but there is no safe or sane way
2968: * for us to continue parsing the format and
2969: * fetching from the va_list; the remaining
2970: * specifiers and arguments would be out of
2971: * sync.
2972: */
2973: goto out;
2974: }
2975: }
2976:
2977: out:
2978: if (size > 0) {
2979: if (str < end)
2980: *str = '\0';
2981: else
2982: end[-1] = '\0';
2983: }
2984:
2985: /* the trailing null byte doesn't count towards the total */
2986: return str-buf;
2987:
2988: }
SourceFile:lib/vsprintf.c]
|
| 46/2 |
2026/05/20 00:12 |
llm |
expert |
0m
Model:
Tokens:
input: 40090
output: 38
thoughts: 1939
Thoughts: **Analyzing a Potential Kernel Crash**
Okay, let's break this down. It looks like `vsnprintf` is writing to an incorrect memory location, specifically overwriting part of a block's `id` field. The address `0xffffffff8936612c` is where the write occurs, which, based on the offset calculations, is leading to a potential overflow.
Initially, I see `vsnprintf` writing to `str`, and I'm correlating this with an observed `memcpy`. The `old_fmt` string "type 2 family 2 port 0 - 0\n" is used, and I'm trying to match the bytes written (7 bytes) with parts of the format string. The fact that "pe 2 fam" is 8 bytes is initially throwing me off because of the KCSAN report. The write is only 7 bytes, and the changed value is 8 bytes. I'm focusing on the literal string components: "type ", the integer, and " family ".
Then, it clicks. The write to `0xffffffff8936612c` is indeed overwriting a part of the next block, and that's the vulnerability. The issue appears to be related to the `blk` structure and how `data_alloc` and `data_make_reusable` interact. Specifically, the offsets within the block are critical. `blk->data` starts at offset 8, implying that `blk->id` is at the beginning of the block.
The key observation is that `vsnprintf` is writing to `0xffffffff8936612c`, which is *before* `blk->id` at `0xffffffff89366130`. This is where the potential overwrite happens. The code in `data_alloc` determines the location of this blk by `to_block` calls. In `data_make_reusable`, the block is located by the variable `lpos_begin`. This means the two blocks are different.
So, the next part of this analysis concerns a possible size calculation flaw in `vsnprintf` or how the string is formatted. The function `vsnprintf` is being used to calculate a string length by writing into `prefix_buf`. I am scrutinizing `%pV` in the format string. I'm checking if the `vsnprintf` used for the `%pV` handling is safe. I'm going to carefully review the implementation of `va_format` in `lib/vsprintf.c` and how it handles the `%pV` specifier to see if there's a potential vulnerability.
|
| 47/2 |
2026/05/20 00:12 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:lib/vsprintf.c IncludeLines:true Name:va_format]
Results: map[SourceCode:1714: static char *va_format(char *buf, char *end, struct va_format *va_fmt,
1715: struct printf_spec spec)
1716: {
1717: va_list va;
1718:
1719: if (check_pointer(&buf, end, va_fmt, spec))
1720: return buf;
1721:
1722: va_copy(va, *va_fmt->va);
1723: buf += vsnprintf(buf, end > buf ? end - buf : 0, va_fmt->fmt, va);
1724: va_end(va);
1725:
1726: return buf;
1727: }
SourceFile:lib/vsprintf.c]
|
| 48/2 |
2026/05/20 00:12 |
llm |
expert |
0m
Model:
Tokens:
input: 42867
output: 53
thoughts: 828
Thoughts: **Analyzing the `vprintk_store` Log Formatting**
Okay, let's break this down step by step. I'm looking at how `va_format` interacts with `vsnprintf` and the potential for off-by-one errors or incorrect length calculations, particularly when dealing with nested format strings.
I see that `va_format` calls `vsnprintf` with the remaining buffer space. If the initial buffer size is zero, as it is during the initial size calculation, `vsnprintf` should handle this gracefully, returning the required size. This is correct.
I need to trace the execution within `vprintk_store`. The critical line is:
```c
reserve_size = vsnprintf(&prefix_buf[0], sizeof(prefix_buf), fmt, args2) + 1;
```
`prefix_buf` is only 8 bytes. `vsnprintf` will write up to 8 bytes, and crucially, return the *total* length required, even if truncation occurs. It looks like `args2` is a copy of the original arguments, `args`. The arguments `args` are passed to the inner `vsnprintf` via a pointer to `struct va_format`. This `struct va_format` then calls `vsnprintf` again.
Here's the critical bit:
```c
va_copy(va, *va_fmt->va);
buf += vsnprintf(buf, end > buf ? end - buf : 0, va_fmt->fmt, va);
va_end(va);
```
This *copies* the `va_list` from the original arguments. `va_fmt->va` points to the `va_list` passed into the initial call to `__netdev_printk`, so `va_copy` makes a copy of the `va_list`, and the nested `vsnprintf` *consumes* arguments from this copy. `va_end` is then called on the copy. Importantly, the original `va_list` is *not* modified.
Now, `vprintk_store` calls `printk_sprint` a second time, after determining `reserve_size`. It passes the *original* arguments (`args`), including the pointer to the `struct va_format`. The code is NOT modifying the original argument list. The second call to `va_format` makes *another* copy.
If the *original* `va_list` wasn't modified in the first call, it means that the arguments for the internal format string are available to the second call to `vsnprintf` as well. In this case, `reserve_size` is calculated correctly, because the length returned by the first `vsnprintf` will be exactly the same as the length returned by the second call.
Wait a minute, is it possible for the *arguments of the inner formatting string* to be consumed? The inner format string is `"unset [%d, %d] type %d family %d port %d - %d\n"`. The arguments for this are passed via a `va_list` in `nsim_udp_tunnel_unset_port`. But since we are making a *copy* of the original argument list, this does not matter. The inner call *won't* have side effects on the arguments to the outer calls, because the argument lists are copied.
Thus, the `reserve_size` calculation should be accurate, and `vsnprintf` should *not* write out of bounds. The code is working correctly as far as I can see. I'm going to double check `nsim_udp_tunnel_unset_port` anyway to see if something unexpected is happening there. But, based on the `va_copy` calls, there shouldn't be a problem here.
|
| 49/2 |
2026/05/20 00:12 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:drivers/net/netdevsim/udp_tunnels.c IncludeLines:true Name:nsim_udp_tunnel_unset_port]
Results: map[SourceCode: 37: static int
38: nsim_udp_tunnel_unset_port(struct net_device *dev, unsigned int table,
39: unsigned int entry, struct udp_tunnel_info *ti)
40: {
41: struct netdevsim *ns = netdev_priv(dev);
42: int ret;
43:
44: ret = -ns->udp_ports.inject_error;
45: ns->udp_ports.inject_error = 0;
46:
47: if (!ret) {
48: u32 val = be16_to_cpu(ti->port) << 16 | ti->type;
49:
50: if (val == ns->udp_ports.ports[table][entry]) {
51: ns->udp_ports.ports[table][entry] = 0;
52: } else {
53: WARN(1, "entry not installed %x vs %x\n",
54: val, ns->udp_ports.ports[table][entry]);
55: ret = -ENOENT;
56: }
57: }
58:
59: netdev_info(dev, "unset [%d, %d] type %d family %d port %d - %d\n",
60: table, entry, ti->type, ti->sa_family, ntohs(ti->port),
61: ret);
62: return ret;
63: }
SourceFile:drivers/net/netdevsim/udp_tunnels.c]
|
| 50/2 |
2026/05/20 00:12 |
llm |
expert |
0m
Model:
Tokens:
input: 45012
output: 41
thoughts: 20
Thoughts: Here's a summary of my thought process:
**Diving into `netdev_info`**
Okay, so I'm seeing `netdev_info` here. It's a macro, of course. My immediate instinct is to take a closer look at it and see exactly what it's doing. Macros can be deceptively simple on the surface, or they can be wrappers for some fairly complex operations, especially in the kernel. I need to understand its expansion to grasp the actual log output, any side effects, or any conditional behavior it might have. So, let's go check the definition of `netdev_info`. Gotta understand the foundations before I can truly grok its usage.
|
| 51/2 |
2026/05/20 00:13 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:include/linux/netdevice.h IncludeLines:true Name:netdev_info]
Results: map[SourceCode:12996: define_netdev_printk_level(netdev_info, KERN_INFO);
SourceFile:net/core/dev.c]
|
| 52/2 |
2026/05/20 00:13 |
llm |
expert |
0m
Model:
Tokens:
input: 45278
output: 45
thoughts: 33
Thoughts: Okay, here's my interpretation of that thought process, as if I were having it:
**Digging into the Kernel Code**
Alright, I'm tracking down the definition of `netdev_info`. My initial thought was that it was likely within the core networking device code, perhaps in `net/core/dev.c`. I mean, that's where a lot of the fundamental device stuff resides, so it seemed like a reasonable starting point. But wait... on second thought, that doesn't feel right... I quickly realized it's more of a general networking device structure, not just the low-level logic. Of course! It's actually likely defined in `include/linux/netdevice.h`. That makes much more sense; it's part of the public interface for dealing with network devices. Okay, I was on the right track, just needed a little course correction!
|
| 53/2 |
2026/05/20 00:13 |
tool |
codesearch-definition-source |
0m
Error: requested entity does not exist
Args: map[ContextFile:include/linux/netdevice.h IncludeLines:true Name:define_netdev_printk_level]
Results: map[SourceCode: SourceFile:]
|
| 54/2 |
2026/05/20 00:13 |
llm |
expert |
0m
Model:
Tokens:
input: 45566
output: 18
thoughts: 11
Thoughts: Here's my thought process, summarized as you requested:
**Grepping for `netdev_info`**
Okay, so I need to find all instances of `netdev_info` in this codebase. My gut tells me that's a good place to start digging for network device-related information. Let's see... a simple `grep "netdev_info"` should do the trick initially. That will give me a first pass at all the locations that are using that function (or variable, or macro β need to keep that flexibility in mind). From there, I can start to refine the search. I can look for specific arguments being passed to the function, see where it's being defined, and trace its usage. The goal is to quickly understand how network device information is handled and exposed within this system. It will also help identify any potential areas that might need attention regarding specific network devices or information pertaining to the network in general.
|
| 55/2 |
2026/05/20 00:13 |
tool |
grepper |
0m
Args: map[Expression:netdev_info]
Results: map[Output:
Full output is too long, showing 500 out of 6043 lines.
Use more precise expression if possible.
[arch/m68k/emu/nfeth.c=185=static struct net_device * __init nfeth_probe(int unit)
--
arch/m68k/emu/nfeth.c-218-
arch/m68k/emu/nfeth.c:219: netdev_info(dev, KBUILD_MODNAME " addr:%s (%s) HWaddr:%pM\n", host_ip,
arch/m68k/emu/nfeth.c-220- local_ip, mac);
--
arch/mips/include/asm/sn/klconfig.h=787=typedef struct klenetdev_s { /* ENET device */
arch/mips/include/asm/sn/klconfig.h:788: klinfo_t enetdev_info ;
arch/mips/include/asm/sn/klconfig.h-789- struct net_data *enetdev_cfg ; /* driver fills up this */
--
arch/um/drivers/vector_kern.c=1538=static void vector_setup_etheraddr(struct net_device *dev, char *str)
--
arch/um/drivers/vector_kern.c-1569-random:
arch/um/drivers/vector_kern.c:1570: netdev_info(dev, "Choosing a random ethernet address\n");
arch/um/drivers/vector_kern.c-1571- eth_hw_addr_random(dev);
--
arch/um/drivers/vector_transports.c=399=static int build_raw_transport_data(struct vector_private *vp)
--
arch/um/drivers/vector_transports.c-411- NETIF_F_TSO | NETIF_F_GRO);
arch/um/drivers/vector_transports.c:412: netdev_info(
arch/um/drivers/vector_transports.c-413- vp->dev,
--
arch/um/drivers/vector_transports.c=420=static int build_hybrid_transport_data(struct vector_private *vp)
--
arch/um/drivers/vector_transports.c-431- NETIF_F_TSO | NETIF_F_GSO | NETIF_F_GRO);
arch/um/drivers/vector_transports.c:432: netdev_info(
arch/um/drivers/vector_transports.c-433- vp->dev,
--
arch/um/drivers/vector_transports.c=444=static int build_tap_transport_data(struct vector_private *vp)
--
arch/um/drivers/vector_transports.c-456- NETIF_F_TSO | NETIF_F_GSO | NETIF_F_GRO);
arch/um/drivers/vector_transports.c:457: netdev_info(
arch/um/drivers/vector_transports.c-458- vp->dev,
--
drivers/infiniband/ulp/ipoib/ipoib_main.c=2549=static ssize_t dev_id_show(struct device *dev,
--
drivers/infiniband/ulp/ipoib/ipoib_main.c-2565- if (ndev->dev_port && ndev->dev_id == ndev->dev_port)
drivers/infiniband/ulp/ipoib/ipoib_main.c:2566: netdev_info_once(ndev,
drivers/infiniband/ulp/ipoib/ipoib_main.c-2567- "\"%s\" wants to know my dev_id. Should it look at dev_port instead? See Documentation/ABI/testing/sysfs-class-net for more info.\n",
--
drivers/net/arcnet/arcdevice.h=81=do { \
--
drivers/net/arcnet/arcdevice.h-85- else if ((x) < D_DURING) \
drivers/net/arcnet/arcdevice.h:86: netdev_info(dev, fmt, ##__VA_ARGS__); \
drivers/net/arcnet/arcdevice.h-87- else \
--
drivers/net/arcnet/arcnet.c=383=static void arcnet_timer(struct timer_list *t)
--
drivers/net/arcnet/arcnet.c-391- netif_carrier_on(dev);
drivers/net/arcnet/arcnet.c:392: netdev_info(dev, "link up\n");
drivers/net/arcnet/arcnet.c-393- }
--
drivers/net/arcnet/arcnet.c=854=irqreturn_t arcnet_interrupt(int irq, void *dev_id)
--
drivers/net/arcnet/arcnet.c-1038- netif_carrier_off(dev);
drivers/net/arcnet/arcnet.c:1039: netdev_info(dev, "link down\n");
drivers/net/arcnet/arcnet.c-1040- }
--
drivers/net/bonding/bond_main.c=1366=void bond_select_active_slave(struct bonding *bond)
--
drivers/net/bonding/bond_main.c-1380- if (netif_carrier_ok(bond->dev))
drivers/net/bonding/bond_main.c:1381: netdev_info(bond->dev, "active interface up!\n");
drivers/net/bonding/bond_main.c-1382- else
drivers/net/bonding/bond_main.c:1383: netdev_info(bond->dev, "now running without any active interface!\n");
drivers/net/bonding/bond_main.c-1384- }
--
drivers/net/bonding/bond_main.c=2602=static int bond_release_and_destroy(struct net_device *bond_dev,
--
drivers/net/bonding/bond_main.c-2611- bond_dev->priv_flags |= IFF_DISABLE_NETPOLL;
drivers/net/bonding/bond_main.c:2612: netdev_info(bond_dev, "Destroying bond\n");
drivers/net/bonding/bond_main.c-2613- bond_remove_proc_entry(bond);
--
drivers/net/bonding/bond_main.c=3746=static bool bond_ab_arp_probe(struct bonding *bond)
--
drivers/net/bonding/bond_main.c-3755- if (curr_arp_slave && curr_active_slave)
drivers/net/bonding/bond_main.c:3756: netdev_info(bond->dev, "PROBE: c_arp %s && cas %s BAD\n",
drivers/net/bonding/bond_main.c-3757- curr_arp_slave->dev->name,
--
drivers/net/bonding/bond_main.c=3929=static int bond_slave_netdev_event(unsigned long event,
--
drivers/net/bonding/bond_main.c-4018-
drivers/net/bonding/bond_main.c:4019: netdev_info(bond->dev, "Primary slave changed to %s, reselecting active slave\n",
drivers/net/bonding/bond_main.c-4020- primary ? slave_dev->name : "none");
--
drivers/net/bonding/bond_main.c=6049=static void bond_uninit(struct net_device *bond_dev)
--
drivers/net/bonding/bond_main.c-6059- __bond_release_one(bond_dev, slave->dev, true, true);
drivers/net/bonding/bond_main.c:6060: netdev_info(bond_dev, "Released all slaves\n");
drivers/net/bonding/bond_main.c-6061-
--
drivers/net/bonding/bond_options.c=1886=static int bond_option_coupled_control_set(struct bonding *bond,
--
drivers/net/bonding/bond_options.c-1888-{
drivers/net/bonding/bond_options.c:1889: netdev_info(bond->dev, "Setting coupled_control to %s (%llu)\n",
drivers/net/bonding/bond_options.c-1890- newval->string, newval->value);
--
drivers/net/can/c_can/c_can_main.c=501=static int c_can_set_bittiming(struct net_device *dev)
--
drivers/net/can/c_can/c_can_main.c-521-
drivers/net/can/c_can/c_can_main.c:522: netdev_info(dev,
drivers/net/can/c_can/c_can_main.c-523- "setting BTR=%04x BRPE=%04x\n", reg_btr, reg_brpe);
--
drivers/net/can/can327.c=1006=static int can327_ldisc_open(struct tty_struct *tty)
--
drivers/net/can/can327.c-1048-
drivers/net/can/can327.c:1049: netdev_info(elm->dev, "can327 on %s.\n", tty->name);
drivers/net/can/can327.c-1050-
--
drivers/net/can/can327.c=1061=static void can327_ldisc_close(struct tty_struct *tty)
--
drivers/net/can/can327.c-1079-
drivers/net/can/can327.c:1080: netdev_info(elm->dev, "can327 off %s.\n", tty->name);
drivers/net/can/can327.c-1081-
--
drivers/net/can/cc770/cc770.c=290=static int cc770_probe_chip(struct net_device *dev)
--
drivers/net/can/cc770/cc770.c-303- if (cc770_read_reg(priv, cpu_interface) & CPUIF_RST) {
drivers/net/can/cc770/cc770.c:304: netdev_info(dev, "probing @0x%p failed (reset)\n",
drivers/net/can/cc770/cc770.c-305- priv->reg_base);
--
drivers/net/can/cc770/cc770.c-315- (cc770_read_reg(priv, msgobj[10].data[6]) != 0xc3)) {
drivers/net/can/cc770/cc770.c:316: netdev_info(dev, "probing @0x%p failed (pattern)\n",
drivers/net/can/cc770/cc770.c-317- priv->reg_base);
--
drivers/net/can/cc770/cc770.c=355=static int cc770_set_bittiming(struct net_device *dev)
--
drivers/net/can/cc770/cc770.c-366-
drivers/net/can/cc770/cc770.c:367: netdev_info(dev, "setting BTR0=0x%02x BTR1=0x%02x\n", btr0, btr1);
drivers/net/can/cc770/cc770.c-368-
--
drivers/net/can/ctucanfd/ctucanfd_base.c=801=static void ctucan_err_interrupt(struct net_device *ndev, u32 isr)
--
drivers/net/can/ctucanfd/ctucanfd_base.c-816- if (dologerr)
drivers/net/can/ctucanfd/ctucanfd_base.c:817: netdev_info(ndev, "%s: ISR = 0x%08x, rxerr %d, txerr %d, error type %lu, pos %lu, ALC id_field %lu, bit %lu\n",
drivers/net/can/ctucanfd/ctucanfd_base.c-818- __func__, isr, bec.rxerr, bec.txerr,
--
drivers/net/can/ctucanfd/ctucanfd_base.c-831- if (FIELD_GET(REG_INT_STAT_FCSI, isr) || FIELD_GET(REG_INT_STAT_EWLI, isr)) {
drivers/net/can/ctucanfd/ctucanfd_base.c:832: netdev_info(ndev, "state changes from %s to %s\n",
drivers/net/can/ctucanfd/ctucanfd_base.c-833- ctucan_state_to_str(priv->can.state),
--
drivers/net/can/ctucanfd/ctucanfd_base.c-887- if (dologerr)
drivers/net/can/ctucanfd/ctucanfd_base.c:888: netdev_info(ndev, "arbitration lost\n");
drivers/net/can/ctucanfd/ctucanfd_base.c-889- priv->can.can_stats.arbitration_lost++;
--
drivers/net/can/ctucanfd/ctucanfd_base.c-897- if (FIELD_GET(REG_INT_STAT_BEI, isr)) {
drivers/net/can/ctucanfd/ctucanfd_base.c:898: netdev_info(ndev, "bus error\n");
drivers/net/can/ctucanfd/ctucanfd_base.c-899- priv->can.can_stats.bus_error++;
--
drivers/net/can/ctucanfd/ctucanfd_base.c=924=static int ctucan_rx_poll(struct napi_struct *napi, int quota)
--
drivers/net/can/ctucanfd/ctucanfd_base.c-946-
drivers/net/can/ctucanfd/ctucanfd_base.c:947: netdev_info(ndev, "rx_poll: rx fifo overflow\n");
drivers/net/can/ctucanfd/ctucanfd_base.c-948- stats->rx_over_errors++;
--
drivers/net/can/ctucanfd/ctucanfd_base.c=1200=static int ctucan_open(struct net_device *ndev)
--
drivers/net/can/ctucanfd/ctucanfd_base.c-1235-
drivers/net/can/ctucanfd/ctucanfd_base.c:1236: netdev_info(ndev, "ctu_can_fd device registered\n");
drivers/net/can/ctucanfd/ctucanfd_base.c-1237- napi_enable(&priv->napi);
--
drivers/net/can/dev/dev.c=264=void can_bus_off(struct net_device *dev)
--
drivers/net/can/dev/dev.c-268- if (priv->restart_ms)
drivers/net/can/dev/dev.c:269: netdev_info(dev, "bus-off, scheduling restart in %d ms\n",
drivers/net/can/dev/dev.c-270- priv->restart_ms);
drivers/net/can/dev/dev.c-271- else
drivers/net/can/dev/dev.c:272: netdev_info(dev, "bus-off\n");
drivers/net/can/dev/dev.c-273-
--
drivers/net/can/esd/esd_402_pci-core.c=327=static void pci402_unregister_core(struct acc_core *core)
drivers/net/can/esd/esd_402_pci-core.c-328-{
drivers/net/can/esd/esd_402_pci-core.c:329: netdev_info(core->netdev, "unregister\n");
drivers/net/can/esd/esd_402_pci-core.c-330- unregister_candev(core->netdev);
--
drivers/net/can/esd/esd_402_pci-core.c=336=static int pci402_init_cores(struct pci_dev *pdev)
--
drivers/net/can/esd/esd_402_pci-core.c-396-
drivers/net/can/esd/esd_402_pci-core.c:397: netdev_info(netdev, "registered\n");
drivers/net/can/esd/esd_402_pci-core.c-398- }
--
drivers/net/can/flexcan/flexcan-ethtool.c=61=static int flexcan_set_priv_flags(struct net_device *ndev, u32 priv_flags)
--
drivers/net/can/flexcan/flexcan-ethtool.c-86- !flexcan_active_rx_rtr(priv))
drivers/net/can/flexcan/flexcan-ethtool.c:87: netdev_info(ndev,
drivers/net/can/flexcan/flexcan-ethtool.c-88- "Activating RX mailbox mode, cannot receive RTR frames.\n");
--
drivers/net/can/grcan.c=405=static int grcan_set_bittiming(struct net_device *dev)
--
drivers/net/can/grcan.c-441- timing |= (scaler << GRCAN_CONF_SCALER_BIT) & GRCAN_CONF_SCALER;
drivers/net/can/grcan.c:442: netdev_info(dev, "setting timing=0x%x\n", timing);
drivers/net/can/grcan.c-443- grcan_write_bits(®s->conf, timing, GRCAN_CONF_TIMING);
--
drivers/net/can/grcan.c=1017=static int grcan_set_mode(struct net_device *dev, enum can_mode mode)
--
drivers/net/can/grcan.c-1030- } else {
drivers/net/can/grcan.c:1031: netdev_info(dev, "Restarting device\n");
drivers/net/can/grcan.c-1032- grcan_start(dev);
--
drivers/net/can/janz-ican3.c=1802=static int ican3_get_berr_counter(const struct net_device *ndev,
--
drivers/net/can/janz-ican3.c-1812- if (!wait_for_completion_timeout(&mod->buserror_comp, HZ)) {
drivers/net/can/janz-ican3.c:1813: netdev_info(mod->ndev, "%s timed out\n", __func__);
drivers/net/can/janz-ican3.c-1814- return -ETIMEDOUT;
--
drivers/net/can/janz-ican3.c=1826=static ssize_t termination_show(struct device *dev,
--
drivers/net/can/janz-ican3.c-1837- if (!wait_for_completion_timeout(&mod->termination_comp, HZ)) {
drivers/net/can/janz-ican3.c:1838: netdev_info(mod->ndev, "%s timed out\n", __func__);
drivers/net/can/janz-ican3.c-1839- return -ETIMEDOUT;
--
drivers/net/can/janz-ican3.c=1889=static int ican3_probe(struct platform_device *pdev)
--
drivers/net/can/janz-ican3.c-2007-
drivers/net/can/janz-ican3.c:2008: netdev_info(mod->ndev, "module %d: registered CAN device\n", pdata->modno);
drivers/net/can/janz-ican3.c-2009- return 0;
--
drivers/net/can/m_can/m_can.c=2508=int m_can_class_register(struct m_can_classdev *cdev)
--
drivers/net/can/m_can/m_can.c-2564-
drivers/net/can/m_can/m_can.c:2565: netdev_info(cdev->net, "device registered (irq=%d, version=%d)\n",
drivers/net/can/m_can/m_can.c-2566- cdev->net->irq, cdev->version);
--
drivers/net/can/m_can/tcan4x5x-core.c=410=static int tcan4x5x_can_probe(struct spi_device *spi)
--
drivers/net/can/m_can/tcan4x5x-core.c-529-
drivers/net/can/m_can/tcan4x5x-core.c:530: netdev_info(mcan_class->net, "TCAN4X5X successfully initialized.\n");
drivers/net/can/m_can/tcan4x5x-core.c-531- return 0;
--
drivers/net/can/mscan/mscan.c=502=static int mscan_do_set_bittiming(struct net_device *dev)
--
drivers/net/can/mscan/mscan.c-513-
drivers/net/can/mscan/mscan.c:514: netdev_info(dev, "setting BTR0=0x%02x BTR1=0x%02x\n", btr0, btr1);
drivers/net/can/mscan/mscan.c-515-
--
drivers/net/can/rockchip/rockchip_canfd-core.c=650=static irqreturn_t rkcanfd_irq(int irq, void *dev_id)
--
drivers/net/can/rockchip/rockchip_canfd-core.c-686- if (reg_int & RKCANFD_REG_INT_WAKEUP_INT)
drivers/net/can/rockchip/rockchip_canfd-core.c:687: netdev_info(priv->ndev, "%s: WAKEUP_INT\n", __func__);
drivers/net/can/rockchip/rockchip_canfd-core.c-688-
drivers/net/can/rockchip/rockchip_canfd-core.c-689- if (reg_int & RKCANFD_REG_INT_TXE_FIFO_FULL_INT)
drivers/net/can/rockchip/rockchip_canfd-core.c:690: netdev_info(priv->ndev, "%s: TXE_FIFO_FULL_INT\n", __func__);
drivers/net/can/rockchip/rockchip_canfd-core.c-691-
drivers/net/can/rockchip/rockchip_canfd-core.c-692- if (reg_int & RKCANFD_REG_INT_TXE_FIFO_OV_INT)
drivers/net/can/rockchip/rockchip_canfd-core.c:693: netdev_info(priv->ndev, "%s: TXE_FIFO_OV_INT\n", __func__);
drivers/net/can/rockchip/rockchip_canfd-core.c-694-
drivers/net/can/rockchip/rockchip_canfd-core.c-695- if (reg_int & RKCANFD_REG_INT_BUS_OFF_RECOVERY_INT)
drivers/net/can/rockchip/rockchip_canfd-core.c:696: netdev_info(priv->ndev, "%s: BUS_OFF_RECOVERY_INT\n", __func__);
drivers/net/can/rockchip/rockchip_canfd-core.c-697-
drivers/net/can/rockchip/rockchip_canfd-core.c-698- if (reg_int & RKCANFD_REG_INT_RX_FIFO_FULL_INT)
drivers/net/can/rockchip/rockchip_canfd-core.c:699: netdev_info(priv->ndev, "%s: RX_FIFO_FULL_INT\n", __func__);
drivers/net/can/rockchip/rockchip_canfd-core.c-700-
drivers/net/can/rockchip/rockchip_canfd-core.c-701- if (reg_int & RKCANFD_REG_INT_OVERLOAD_INT)
drivers/net/can/rockchip/rockchip_canfd-core.c:702: netdev_info(priv->ndev, "%s: OVERLOAD_INT\n", __func__);
drivers/net/can/rockchip/rockchip_canfd-core.c-703-
--
drivers/net/can/rockchip/rockchip_canfd-core.c=782=static void rkcanfd_register_done(const struct rkcanfd_priv *priv)
--
drivers/net/can/rockchip/rockchip_canfd-core.c-787-
drivers/net/can/rockchip/rockchip_canfd-core.c:788: netdev_info(priv->ndev,
drivers/net/can/rockchip/rockchip_canfd-core.c-789- "Rockchip-CANFD %s rev%lu.%lu (errata 0x%04x) found\n",
--
drivers/net/can/rockchip/rockchip_canfd-core.c-796- priv->can.clock.freq < RKCANFD_ERRATUM_5_SYSCLOCK_HZ_MIN)
drivers/net/can/rockchip/rockchip_canfd-core.c:797: netdev_info(priv->ndev,
drivers/net/can/rockchip/rockchip_canfd-core.c-798- "Erratum 5: CAN clock frequency (%luMHz) lower than known good (%luMHz), expect degraded performance\n",
--
drivers/net/can/rockchip/rockchip_canfd-tx.c=66=netdev_tx_t rkcanfd_start_xmit(struct sk_buff *skb, struct net_device *ndev)
--
drivers/net/can/rockchip/rockchip_canfd-tx.c-82- if (net_ratelimit())
drivers/net/can/rockchip/rockchip_canfd-tx.c:83: netdev_info(priv->ndev,
drivers/net/can/rockchip/rockchip_canfd-tx.c-84- "Stopping tx-queue (tx_head=0x%08x, tx_tail=0x%08x, tx_pending=%d)\n",
--
drivers/net/can/sja1000/sja1000.c=246=static int sja1000_set_bittiming(struct net_device *dev)
--
drivers/net/can/sja1000/sja1000.c-257-
drivers/net/can/sja1000/sja1000.c:258: netdev_info(dev, "setting BTR0=0x%02x BTR1=0x%02x\n", btr0, btr1);
drivers/net/can/sja1000/sja1000.c-259-
--
drivers/net/can/sja1000/tscan1.c=78=static int tscan1_probe(struct device *dev, unsigned id)
--
drivers/net/can/sja1000/tscan1.c-143- outb(0, pld_base + TSCAN1_LED);
drivers/net/can/sja1000/tscan1.c:144: netdev_info(netdev, "TS-CAN1 at 0x%lx 0x%lx irq %d\n",
drivers/net/can/sja1000/tscan1.c-145- pld_base, sja1000_base, irq);
--
drivers/net/can/slcan/slcan-core.c=817=static int slcan_open(struct tty_struct *tty)
--
drivers/net/can/slcan/slcan-core.c-863-
drivers/net/can/slcan/slcan-core.c:864: netdev_info(dev, "slcan on %s.\n", tty->name);
drivers/net/can/slcan/slcan-core.c-865- /* TTY layer expects 0 on success */
--
drivers/net/can/slcan/slcan-core.c=876=static void slcan_close(struct tty_struct *tty)
--
drivers/net/can/slcan/slcan-core.c-893-
drivers/net/can/slcan/slcan-core.c:894: netdev_info(sl->dev, "slcan off %s.\n", tty->name);
drivers/net/can/slcan/slcan-core.c-895- free_candev(sl->dev);
--
drivers/net/can/spi/hi311x.c=829=static int hi3110_can_probe(struct spi_device *spi)
--
drivers/net/can/spi/hi311x.c-940-
drivers/net/can/spi/hi311x.c:941: netdev_info(net, "%x successfully initialized.\n", priv->model);
drivers/net/can/spi/hi311x.c-942-
--
drivers/net/can/spi/mcp251x.c=1331=static int mcp251x_can_probe(struct spi_device *spi)
--
drivers/net/can/spi/mcp251x.c-1455-
drivers/net/can/spi/mcp251x.c:1456: netdev_info(net, "MCP%x successfully initialized.\n", priv->model);
drivers/net/can/spi/mcp251x.c-1457- return 0;
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c=425=static int mcp251xfd_chip_softreset_check(const struct mcp251xfd_priv *priv)
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-446- if (mode != MCP251XFD_REG_CON_MODE_CONFIG) {
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c:447: netdev_info(priv->ndev,
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-448- "Controller not in Config Mode after reset, but in %s Mode (%u).\n",
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c=456=static int mcp251xfd_chip_softreset(const struct mcp251xfd_priv *priv)
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-461- if (i)
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c:462: netdev_info(priv->ndev,
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-463- "Retrying to reset controller.\n");
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c=983=static int mcp251xfd_handle_txatif(struct mcp251xfd_priv *priv)
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-984-{
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c:985: netdev_info(priv->ndev, "%s\n", __func__);
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-986-
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c=1217=static int mcp251xfd_handle_serrif(struct mcp251xfd_priv *priv)
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-1259- else
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c:1260: netdev_info(priv->ndev, "%s\n", msg);
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-1261-
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c=1296=mcp251xfd_handle_eccif_recover(struct mcp251xfd_priv *priv, u8 nr)
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-1328-
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c:1329: netdev_info(priv->ndev,
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-1330- "Recovering %s ECC Error at address 0x%04x (in TX-RAM, tx_obj=%d, tx_tail=0x%08x(%d), offset=%d).\n",
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c=1346=mcp251xfd_handle_eccif(struct mcp251xfd_priv *priv, bool set_normal_mode)
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-1407-
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c:1408: netdev_info(priv->ndev,
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-1409- "%s 0x%04x (in TX-RAM, tx_obj=%d), occurred %d time%s.\n",
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c=1751=static int mcp251xfd_register_chip_detect(struct mcp251xfd_priv *priv)
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-1785- priv->devtype_data.model != devtype_data->model) {
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c:1786: netdev_info(ndev,
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-1787- "Detected %s, but firmware specifies a %s. Fixing up.\n",
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c=1800=static int mcp251xfd_register_check_rx_int(struct mcp251xfd_priv *priv)
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-1822-
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c:1823: netdev_info(priv->ndev,
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-1824- "RX_INT active after softreset, disabling RX_INT support.\n");
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c=2039=mcp251xfd_register_done(const struct mcp251xfd_priv *priv)
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-2052-
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c:2053: netdev_info(priv->ndev,
drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c-2054- "%s rev%lu.%lu (%cRX_INT %cPLL %cMAB_NO_WARN %cCRC_REG %cCRC_RX %cCRC_TX %cECC %cHD o:%lu.%02luMHz c:%u.%02uMHz m:%u.%02uMHz rs:%u.%02uMHz es:%u.%02uMHz rf:%u.%02uMHz ef:%u.%02uMHz) successfully initialized.\n",
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-regmap.c=360=mcp251xfd_regmap_crc_read(void *context,
--
drivers/net/can/spi/mcp251xfd/mcp251xfd-regmap.c-463-
drivers/net/can/spi/mcp251xfd/mcp251xfd-regmap.c:464: netdev_info(priv->ndev,
drivers/net/can/spi/mcp251xfd/mcp251xfd-regmap.c-465- "CRC read error at address 0x%04x (length=%zd, data=%*ph, CRC=0x%04x) retrying.\n",
--
drivers/net/can/ti_hecc.c=255=static int ti_hecc_set_btc(struct ti_hecc_priv *priv)
--
drivers/net/can/ti_hecc.c-275- hecc_write(priv, HECC_CANBTC, can_btc);
drivers/net/can/ti_hecc.c:276: netdev_info(priv->ndev, "setting CANBTC=%#x\n", can_btc);
drivers/net/can/ti_hecc.c-277-
--
drivers/net/can/usb/ems_usb.c=262=static void ems_usb_read_interrupt_callback(struct urb *urb)
--
drivers/net/can/usb/ems_usb.c-286- default:
drivers/net/can/usb/ems_usb.c:287: netdev_info(netdev, "Rx interrupt aborted %d\n", urb->status);
drivers/net/can/usb/ems_usb.c-288- break;
--
drivers/net/can/usb/ems_usb.c=415=static void ems_usb_read_bulk_callback(struct urb *urb)
--
drivers/net/can/usb/ems_usb.c-433- default:
drivers/net/can/usb/ems_usb.c:434: netdev_info(netdev, "Rx URB aborted (%d)\n", urb->status);
drivers/net/can/usb/ems_usb.c-435- goto resubmit_urb;
--
drivers/net/can/usb/ems_usb.c=512=static void ems_usb_write_bulk_callback(struct urb *urb)
--
drivers/net/can/usb/ems_usb.c-532- if (urb->status)
drivers/net/can/usb/ems_usb.c:533: netdev_info(netdev, "Tx URB aborted (%d)\n", urb->status);
drivers/net/can/usb/ems_usb.c-534-
--
drivers/net/can/usb/ems_usb.c=937=static int ems_usb_set_bittiming(struct net_device *netdev)
--
drivers/net/can/usb/ems_usb.c-948-
drivers/net/can/usb/ems_usb.c:949: netdev_info(netdev, "setting BTR0=0x%02x BTR1=0x%02x\n", btr0, btr1);
drivers/net/can/usb/ems_usb.c-950-
--
drivers/net/can/usb/esd_usb.c=567=static void esd_usb_write_bulk_callback(struct urb *urb)
--
drivers/net/can/usb/esd_usb.c-586- if (urb->status)
drivers/net/can/usb/esd_usb.c:587: netdev_info(netdev, "Tx URB aborted (%pe)\n", ERR_PTR(urb->status));
drivers/net/can/usb/esd_usb.c-588-
--
drivers/net/can/usb/esd_usb.c=1206=static int esd_usb_probe_one_net(struct usb_interface *intf, int index)
--
drivers/net/can/usb/esd_usb.c-1282- dev->nets[index] = priv;
drivers/net/can/usb/esd_usb.c:1283: netdev_info(netdev, "registered\n");
drivers/net/can/usb/esd_usb.c-1284-
--
drivers/net/can/usb/esd_usb.c=1374=static void esd_usb_disconnect(struct usb_interface *intf)
--
drivers/net/can/usb/esd_usb.c-1390- netdev = dev->nets[i]->netdev;
drivers/net/can/usb/esd_usb.c:1391: netdev_info(netdev, "unregister\n");
drivers/net/can/usb/esd_usb.c-1392- unregister_netdev(netdev);
--
drivers/net/can/usb/etas_es58x/es581_4.c=95=static int es581_4_rx_can_msg(struct es58x_device *es58x_dev,
--
drivers/net/can/usb/etas_es58x/es581_4.c-115- if (net_ratelimit())
drivers/net/can/usb/etas_es58x/es581_4.c:116: netdev_info(netdev,
drivers/net/can/usb/etas_es58x/es581_4.c-117- "%s: %s is down, dropping %d rx packets\n",
--
drivers/net/can/usb/etas_es58x/es58x_core.c=382=int es58x_can_get_echo_skb(struct net_device *netdev, u32 rcv_packet_idx,
--
drivers/net/can/usb/etas_es58x/es58x_core.c-392- if (net_ratelimit())
drivers/net/can/usb/etas_es58x/es58x_core.c:393: netdev_info(netdev,
drivers/net/can/usb/etas_es58x/es58x_core.c-394- "%s: %s is down, dropping %d echo packets\n",
--
drivers/net/can/usb/etas_es58x/es58x_core.c=658=int es58x_rx_err_msg(struct net_device *netdev, enum es58x_err error,
--
drivers/net/can/usb/etas_es58x/es58x_core.c-669- if (net_ratelimit())
drivers/net/can/usb/etas_es58x/es58x_core.c:670: netdev_info(netdev, "%s: %s is down, dropping packet\n",
drivers/net/can/usb/etas_es58x/es58x_core.c-671- __func__, netdev->name);
--
drivers/net/can/usb/etas_es58x/es58x_core.c-866- priv->err_passive_before_rtx_success == ES58X_CONSECUTIVE_ERR_PASSIVE_MAX) {
drivers/net/can/usb/etas_es58x/es58x_core.c:867: netdev_info(netdev,
drivers/net/can/usb/etas_es58x/es58x_core.c-868- "Got %d consecutive warning events with no successful RX or TX. Forcing bus-off\n",
--
drivers/net/can/usb/etas_es58x/es58x_core.c=970=int es58x_rx_cmd_ret_u32(struct net_device *netdev,
--
drivers/net/can/usb/etas_es58x/es58x_core.c-984- netif_wake_queue(netdev);
drivers/net/can/usb/etas_es58x/es58x_core.c:985: netdev_info(netdev,
drivers/net/can/usb/etas_es58x/es58x_core.c-986- "%s: %s (Serial Number %s): CAN%d channel becomes ready\n",
--
drivers/net/can/usb/etas_es58x/es58x_core.c-1015- if (cmd_ret_type == ES58X_RET_TYPE_DISABLE_CHANNEL) {
drivers/net/can/usb/etas_es58x/es58x_core.c:1016: netdev_info(netdev,
drivers/net/can/usb/etas_es58x/es58x_core.c-1017- "%s: channel is already closed\n", ret_desc);
--
drivers/net/can/usb/etas_es58x/es58x_core.c=1496=static void es58x_write_bulk_callback(struct urb *urb)
--
drivers/net/can/usb/etas_es58x/es58x_core.c-1523- if (net_ratelimit())
drivers/net/can/usb/etas_es58x/es58x_core.c:1524: netdev_info(netdev, "%s: error %pe\n",
drivers/net/can/usb/etas_es58x/es58x_core.c-1525- __func__, ERR_PTR(urb->status));
--
drivers/net/can/usb/etas_es58x/es58x_fd.c=98=static int es58x_fd_rx_can_msg(struct net_device *netdev,
--
drivers/net/can/usb/etas_es58x/es58x_fd.c-158- if (net_ratelimit())
drivers/net/can/usb/etas_es58x/es58x_fd.c:159: netdev_info(netdev,
drivers/net/can/usb/etas_es58x/es58x_fd.c-160- "%s: %s is down, dropping %d rx packets\n",
--
drivers/net/can/usb/f81604.c=412=static void f81604_read_bulk_callback(struct urb *urb)
--
drivers/net/can/usb/f81604.c-422- if (urb->status)
drivers/net/can/usb/f81604.c:423: netdev_info(netdev, "%s: URB aborted %pe\n", __func__,
drivers/net/can/usb/f81604.c-424- ERR_PTR(urb->status));
--
drivers/net/can/usb/f81604.c=613=static void f81604_read_int_callback(struct urb *urb)
--
drivers/net/can/usb/f81604.c-625- if (urb->status)
drivers/net/can/usb/f81604.c:626: netdev_info(netdev, "%s: Int URB aborted: %pe\n", __func__,
drivers/net/can/usb/f81604.c-627- ERR_PTR(urb->status));
--
drivers/net/can/usb/gs_usb.c=609=static void gs_usb_receive_bulk_callback(struct urb *urb)
--
drivers/net/can/usb/gs_usb.c-769- } else if (rc != -ESHUTDOWN && net_ratelimit()) {
drivers/net/can/usb/gs_usb.c:770: netdev_info(netdev, "failed to re-submit IN URB: %pe\n",
drivers/net/can/usb/gs_usb.c-771- ERR_PTR(rc));
--
drivers/net/can/usb/gs_usb.c=815=static void gs_usb_xmit_callback(struct urb *urb)
--
drivers/net/can/usb/gs_usb.c-824- if (urb->status != -ESHUTDOWN && net_ratelimit())
drivers/net/can/usb/gs_usb.c:825: netdev_info(netdev, "failed to xmit URB %u: %pe\n",
drivers/net/can/usb/gs_usb.c-826- txc->echo_id, ERR_PTR(urb->status));
--
drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c=641=static void kvaser_usb_write_bulk_callback(struct urb *urb)
--
drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c-658- if (urb->status)
drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c:659: netdev_info(netdev, "Tx URB aborted (%d)\n", urb->status);
drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c-660-}
--
drivers/net/can/usb/mcba_usb.c=219=static void mcba_usb_write_bulk_callback(struct urb *urb)
--
drivers/net/can/usb/mcba_usb.c-241- if (urb->status)
drivers/net/can/usb/mcba_usb.c:242: netdev_info(netdev, "Tx URB aborted (%d)\n", urb->status);
drivers/net/can/usb/mcba_usb.c-243-
--
drivers/net/can/usb/mcba_usb.c=460=static void mcba_usb_process_ka_usb(struct mcba_priv *priv,
--
drivers/net/can/usb/mcba_usb.c-463- if (unlikely(priv->usb_ka_first_pass)) {
drivers/net/can/usb/mcba_usb.c:464: netdev_info(priv->netdev, "PIC USB version %u.%u\n",
drivers/net/can/usb/mcba_usb.c-465- msg->soft_ver_major, msg->soft_ver_minor);
--
]
]
|
| 56/2 |
2026/05/20 00:13 |
llm |
expert |
0m
Model:
Tokens:
input: 59441
output: 41
thoughts: 198
Thoughts: **Dissecting the `netdev_info` Macro**
Okay, so I'm looking at `netdev_info`, and it's right there in `include/linux/netdevice.h`. Standard stuff, a macro. It's defined as a wrapper around `netdev_printk`, which is a good clue. Let's see...
Aha! `netdev_printk` itself is another macro, and it's the one doing the heavy lifting. It's calling `__netdev_printk`, but it also sets up a `va_format` struct and, crucially, seems to handle variable arguments. Wait a minute... that `vaf.va = &args;` part is interesting. Looks like the `netdev_printk` macro is using `va_start` and `va_end` under the hood! Which means it's properly handling the variable argument list (`...`) passed to `netdev_info`. I should probably double-check that `netdev_printk` is indeed correctly managing `va_list` and not doing anything fishy. Time to dig a little deeper into the `netdev_printk` definition to make sure there are no surprises.
|
| 57/2 |
2026/05/20 00:13 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:include/linux/netdevice.h IncludeLines:true Name:netdev_printk]
Results: map[SourceCode:12956: void netdev_printk(const char *level, const struct net_device *dev,
12957: const char *format, ...)
12958: {
12959: struct va_format vaf;
12960: va_list args;
12961:
12962: va_start(args, format);
12963:
12964: vaf.fmt = format;
12965: vaf.va = &args;
12966:
12967: __netdev_printk(level, dev, &vaf);
12968:
12969: va_end(args);
12970: }
SourceFile:net/core/dev.c]
|
| 58/2 |
2026/05/20 00:13 |
llm |
expert |
0m
Model:
Tokens:
input: 60169
output: 42
thoughts: 3167
Thoughts: **Data Race in `vsnprintf` Within `netdev_printk`**
Okay, so `netdev_printk` is a function that uses `vsnprintf` to format log messages, and I've stumbled upon a data race issue. The trace leads me through a sequence of calls: `netdev_printk` -> `__netdev_printk` -> `dev_printk_emit` -> `vprintk_emit` -> `vprintk_store` -> `printk_sprint` -> `vscnprintf` -> `vsnprintf`.
The core problem seems to be in the double call to `vsnprintf`. The first call determines the required buffer size, and the second call actually performs the formatting. The critical part is how arguments for the format string, especially a variable argument list (`%pV`), are handled with a copy using `va_copy`. It's vital the arguments are NEVER modified by the process.
The KCSAN report pinpoints the write in `vsnprintf` to an address that is four bytes before the aligned read in `data_push_tail` ( specifically from `data_make_reusable` ). This means the read and write are in different memory spaces.
I'm thinking about the layout of the `blk` structure involved. `blk` seems to have an `id` field and a `data` buffer. The race occurs because `data_push_tail` is reading `blk->id` at address `...30`, while `vsnprintf` is writing to `...2c`. The `vsnprintf` function is writing at the wrong offset. It's writing before the block, it writes to `prefix_buf`.
Let me think about that. Why would the buffer, text being passed to `vscnprintf`, be offset in that way? If it's not the same block, what is the connection? The addresses overlap, then it's a completely different block being read and written to, so the blocks must be sequential in memory. The problem is the `reserve_size` value that is first computed.
I suspect the content of one or more of the arguments to `vsnprintf` might be changing between the size calculation and the actual formatting. `netdev_reg_state(dev)` is a string that changes between the first and the second call.
|
| 59/2 |
2026/05/20 00:13 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:net/core/dev.c IncludeLines:true Name:netdev_reg_state]
Results: map[SourceCode:1791: enum netdev_reg_state {
1792: NETREG_UNINITIALIZED = 0,
1793: NETREG_REGISTERED, /* completed register_netdevice */
1794: NETREG_UNREGISTERING, /* called unregister_netdevice */
1795: NETREG_UNREGISTERED, /* completed unregister todo */
1796: NETREG_RELEASED, /* called free_netdev */
1797: NETREG_DUMMY, /* dummy device for NAPI poll */
1798: };
SourceFile:include/linux/netdevice.h]
|
| 60/2 |
2026/05/20 00:13 |
llm |
expert |
1m
Model:
Tokens:
input: 64056
output: 20
thoughts: 54
Thoughts: **Decoding the `netdev_reg_state` Enigma**
Okay, hold on a minute. I'm looking at this code, and something's not quite clicking. `netdev_reg_state` is defined as an enum, right? That much is clear. But then I see this function or macro β or something β also called `netdev_reg_state(dev)` that seems to be *returning a string*! That's... unexpected. Enums are typically associated with integer values, not character strings. My expert instincts are tingling; something doesn't align. I need to get to the bottom of this. Therefore I am going to search for instances of `netdev_reg_state` specifically returning a string. Gotta figure out how this is working and if it's potentially causing some kind of issue. Time to dig!
|
| 61/2 |
2026/05/20 00:14 |
tool |
grepper |
0m
Args: map[Expression:netdev_reg_state]
Results: map[Output:include/linux/netdevice.h=1784=enum netdev_stat_type {
--
include/linux/netdevice.h-1790-
include/linux/netdevice.h:1791:enum netdev_reg_state {
include/linux/netdevice.h-1792- NETREG_UNINITIALIZED = 0,
--
include/linux/netdevice.h=5646=static inline const char *netdev_name(const struct net_device *dev)
--
include/linux/netdevice.h-5652-
include/linux/netdevice.h:5653:static inline const char *netdev_reg_state(const struct net_device *dev)
include/linux/netdevice.h-5654-{
--
include/linux/netdevice.h-5679- WARN(1, "netdevice: %s%s: " format, netdev_name(dev), \
include/linux/netdevice.h:5680: netdev_reg_state(dev), ##args)
include/linux/netdevice.h-5681-
--
include/linux/netdevice.h-5683- WARN_ONCE(1, "netdevice: %s%s: " format, netdev_name(dev), \
include/linux/netdevice.h:5684: netdev_reg_state(dev), ##args)
include/linux/netdevice.h-5685-
--
lib/dynamic_debug.c=916=void __dynamic_netdev_dbg(struct _ddebug *descriptor,
--
lib/dynamic_debug.c-937- dev_name(dev->dev.parent),
lib/dynamic_debug.c:938: netdev_name(dev), netdev_reg_state(dev),
lib/dynamic_debug.c-939- &vaf);
--
lib/dynamic_debug.c-941- printk(KERN_DEBUG "%s%s: %pV", netdev_name(dev),
lib/dynamic_debug.c:942: netdev_reg_state(dev), &vaf);
lib/dynamic_debug.c-943- } else {
--
net/core/dev.c=12937=static void __netdev_printk(const char *level, const struct net_device *dev,
--
net/core/dev.c-12945- dev_name(dev->dev.parent),
net/core/dev.c:12946: netdev_name(dev), netdev_reg_state(dev),
net/core/dev.c-12947- vaf);
--
net/core/dev.c-12949- printk("%s%s%s: %pV",
net/core/dev.c:12950: level, netdev_name(dev), netdev_reg_state(dev), vaf);
net/core/dev.c-12951- } else {
]
|
| 62/2 |
2026/05/20 00:14 |
llm |
expert |
0m
Model:
Tokens:
input: 65079
output: 43
thoughts: 23
Thoughts: Here's my thought process, as if I were considering this myself:
**Investigating Network Device Registration State**
Okay, so I need to understand something related to network device registration. The obvious first step is to dive into the kernel header files. Let's start by checking the `netdev_reg_state` definition, that should be in `include/linux/netdevice.h`. That's where I'd expect to find the fundamental structure or enum that describes the various states a network device can be in during its registration lifecycle. This file is the central source for network device definitions, so `netdev_reg_state` should give me the core idea of what states are possible, and probably some associated macros or constants that represent those states. Understanding the states is the key here. Now to go look.
|
| 63/2 |
2026/05/20 00:14 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:include/linux/netdevice.h IncludeLines:true Name:netdev_reg_state]
Results: map[SourceCode:5653: static inline const char *netdev_reg_state(const struct net_device *dev)
5654: {
5655: u8 reg_state = READ_ONCE(dev->reg_state);
5656:
5657: switch (reg_state) {
5658: case NETREG_UNINITIALIZED: return " (uninitialized)";
5659: case NETREG_REGISTERED: return "";
5660: case NETREG_UNREGISTERING: return " (unregistering)";
5661: case NETREG_UNREGISTERED: return " (unregistered)";
5662: case NETREG_RELEASED: return " (released)";
5663: case NETREG_DUMMY: return " (dummy)";
5664: }
5665:
5666: WARN_ONCE(1, "%s: unknown reg_state %d\n", dev->name, reg_state);
5667: return " (unknown)";
5668: }
SourceFile:include/linux/netdevice.h]
|
| 64/2 |
2026/05/20 00:14 |
llm |
expert |
0m
Model:
Tokens:
input: 65615
output: 44
thoughts: 2138
Thoughts: **Debugging a Potential Data Race in `vsnprintf`**
Okay, so I'm diving into this KCSAN report. The crux of the issue seems to be a potential data race between `vsnprintf` and `data_make_reusable`. My initial thought was, surely `vsnprintf` can't write out of bounds, especially given the explicit bounds checks with `size` and the `end` pointer. I went through the code and confirmed that `vsnprintf` *should* always respect the allocated buffer size (`reserve_size`). The allocation using `prb_reserve` and `data_alloc` also seems sound, with alignment ensuring that the allocated block is large enough to contain the formatted output. I even walked through the alignment calculation with `to_blk_size`, confirming that the actual available space is at least as large as the reported `reserve_size`.
But the KCSAN report persists. It says `vsnprintf` is writing 7 bytes at a specific address while `data_make_reusable` is reading 8 bytes at a close-by address. The addresses overlap, which is the key to the race. I had to go back to the code and really think. The core of the problem is likely `memcpy` within `vsnprintf`. KCSAN reports memory accesses at the granularity of the underlying operation. Since there's a memcpy involved, that's what's being reported, even if it's within the bounds of the allocated buffer. I figured out that since a `memcpy` is being reported as 7 bytes, a literal string is likely being copied.
But the confusion stems from the fact that the `data_make_reusable` function is reading `blk->id` at an offset. This must be the problem. The issue is likely that `data_make_reusable` *thinks* there is a data block at an incorrect starting location, but in reality, there's a block *before* that point. This could be due to misalignment or something within the block metadata. If `vsnprintf` is writing to an offset within its allocated block, and `data_make_reusable` is reading from *another* offset, thatβs where the race is occurring. The data race arises due to the interleaving of these writes and reads, all within an incorrectly assumed allocation! The root cause lies in how the block metadata is handled, especially in relation to how `data_make_reusable` determines the block's starting point from its reported location. I need to focus on where `lpos_begin` comes from and how it's used within `data_make_reusable` to see if a calculation error could result in the incorrect block start location.
|
| 65/2 |
2026/05/20 00:15 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:kernel/printk/printk_ringbuffer.c IncludeLines:true Name:data_push_tail]
Results: map[SourceCode: 645: /*
646: * Advance the data ring tail to at least @lpos. This function puts
647: * descriptors into the reusable state if the tail is pushed beyond
648: * their associated data block.
649: */
650: static bool data_push_tail(struct printk_ringbuffer *rb, unsigned long lpos)
651: {
652: struct prb_data_ring *data_ring = &rb->text_data_ring;
653: unsigned long tail_lpos_new;
654: unsigned long tail_lpos;
655: unsigned long next_lpos;
656:
657: /* If @lpos is from a data-less block, there is nothing to do. */
658: if (LPOS_DATALESS(lpos))
659: return true;
660:
661: /*
662: * Any descriptor states that have transitioned to reusable due to the
663: * data tail being pushed to this loaded value will be visible to this
664: * CPU. This pairs with data_push_tail:D.
665: *
666: * Memory barrier involvement:
667: *
668: * If data_push_tail:A reads from data_push_tail:D, then this CPU can
669: * see desc_make_reusable:A.
670: *
671: * Relies on:
672: *
673: * MB from desc_make_reusable:A to data_push_tail:D
674: * matches
675: * READFROM from data_push_tail:D to data_push_tail:A
676: * thus
677: * READFROM from desc_make_reusable:A to this CPU
678: */
679: tail_lpos = atomic_long_read(&data_ring->tail_lpos); /* LMM(data_push_tail:A) */
680:
681: /*
682: * Loop until the tail lpos is at or beyond @lpos. This condition
683: * may already be satisfied, resulting in no full memory barrier
684: * from data_push_tail:D being performed. However, since this CPU
685: * sees the new tail lpos, any descriptor states that transitioned to
686: * the reusable state must already be visible.
687: */
688: while (need_more_space(data_ring, tail_lpos, lpos)) {
689: /*
690: * Make all descriptors reusable that are associated with
691: * data blocks before @lpos.
692: */
693: if (!data_make_reusable(rb, tail_lpos, lpos, &next_lpos)) {
694: /*
695: * 1. Guarantee the block ID loaded in
696: * data_make_reusable() is performed before
697: * reloading the tail lpos. The failed
698: * data_make_reusable() may be due to a newly
699: * recycled data area causing the tail lpos to
700: * have been previously pushed. This pairs with
701: * data_alloc:A and data_realloc:A.
702: *
703: * Memory barrier involvement:
704: *
705: * If data_make_reusable:A reads from data_alloc:B,
706: * then data_push_tail:C reads from
707: * data_push_tail:D.
708: *
709: * Relies on:
710: *
711: * MB from data_push_tail:D to data_alloc:B
712: * matching
713: * RMB from data_make_reusable:A to
714: * data_push_tail:C
715: *
716: * Note: data_push_tail:D and data_alloc:B can be
717: * different CPUs. However, the data_alloc:B
718: * CPU (which performs the full memory
719: * barrier) must have previously seen
720: * data_push_tail:D.
721: *
722: * 2. Guarantee the descriptor state loaded in
723: * data_make_reusable() is performed before
724: * reloading the tail lpos. The failed
725: * data_make_reusable() may be due to a newly
726: * recycled descriptor causing the tail lpos to
727: * have been previously pushed. This pairs with
728: * desc_reserve:D.
729: *
730: * Memory barrier involvement:
731: *
732: * If data_make_reusable:B reads from
733: * desc_reserve:F, then data_push_tail:C reads
734: * from data_push_tail:D.
735: *
736: * Relies on:
737: *
738: * MB from data_push_tail:D to desc_reserve:F
739: * matching
740: * RMB from data_make_reusable:B to
741: * data_push_tail:C
742: *
743: * Note: data_push_tail:D and desc_reserve:F can
744: * be different CPUs. However, the
745: * desc_reserve:F CPU (which performs the
746: * full memory barrier) must have previously
747: * seen data_push_tail:D.
748: */
749: smp_rmb(); /* LMM(data_push_tail:B) */
750:
751: tail_lpos_new = atomic_long_read(&data_ring->tail_lpos
752: ); /* LMM(data_push_tail:C) */
753: if (tail_lpos_new == tail_lpos)
754: return false;
755:
756: /* Another CPU pushed the tail. Try again. */
757: tail_lpos = tail_lpos_new;
758: continue;
759: }
760:
761: /*
762: * Guarantee any descriptor states that have transitioned to
763: * reusable are stored before pushing the tail lpos. A full
764: * memory barrier is needed since other CPUs may have made
765: * the descriptor states reusable. This pairs with
766: * data_push_tail:A.
767: */
768: if (atomic_long_try_cmpxchg(&data_ring->tail_lpos, &tail_lpos,
769: next_lpos)) { /* LMM(data_push_tail:D) */
770: break;
771: }
772: }
773:
774: return true;
775: }
SourceFile:kernel/printk/printk_ringbuffer.c]
|
| 66/2 |
2026/05/20 00:15 |
llm |
expert |
0m
Model:
Tokens:
input: 70475
output: 45
thoughts: 2465
Thoughts: **Analyzing a Potential Data Race in a Ring Buffer Implementation**
Okay, let's break this down. It seems we have a potential data race issue arising from concurrent access to a ring buffer in this code. The core problem appears to be a race condition involving `data_alloc`, which calls `data_push_tail`, and another process using `vsnprintf` to write data.
My initial thought is to examine how `data_push_tail` is called. It's used to free up space in the ring buffer by pushing the tail pointer. The key here is the calculation `next_lpos - DATA_SIZE(data_ring)`, which essentially calculates where the tail should move to. The crucial part is the potential for CPU 0 (the allocating process) to try and move the tail while CPU 1 (writing using `vsnprintf`) is *also* operating on the buffer.
The text points out a scenario where if the ring buffer is full, `tail_lpos` and `begin_lpos` (where the new block is being written) can map to the same physical offset because of the circular nature of the buffer. This is because `DATA_INDEX` uses a bitwise AND. However, it looks like `data_push_tail` is called BEFORE the block is actually allocated, so `tail_lpos` should *always* be past `begin_lpos`.
But, if CPU 0 is also trying to allocate, it reads `head_lpos` (updated by CPU 1), calculates a `next_lpos_0` and then attempts to push the tail to `next_lpos_0 - DATA_SIZE(data_ring)`. If *that* new tail position is greater than the current `tail_lpos`, then CPU 0 will try and move the tail.
The concern arises if `tail_lpos` could map to the same physical location as `next_lpos`, which is where CPU 1 is writing. This shouldn't happen, right? The block sizes and offsets should be distinct...unless... the buffer wraps around.
If the buffer *does* wrap, then `is_blk_wrapped` is true and the block might start at offset 0. CPU 1 is writing to offset 8 in `blk->data`, and CPU 0 reads `blk->id` at offset 0.
However, the report shows a potential overlap. It tells us CPU 1 is writing to `...2c` (7 bytes) while CPU 0 is reading from `...30`. The overlap at `...30`, `...31`, `...32` is where the concern lies. Now, something is not adding up.
The first potential problem is that `blk->id` is at `...30`, and `blk->data` is at `...38`. But it says the write goes to `...2c`. Could it be that `blk->data` *isn't* at `...38`? Let's consider `struct prb_data_block`. On a 32-bit system, `unsigned long` is 4 bytes, so `data` would be at offset 4. But we're on a 64-bit system, since we see a 64-bit value changing, and a 64-bit system call. This means `unsigned long` is 8 bytes. That would mean `blk->data` *should* be at offset 8. So if `blk` starts at `...30`, then `blk->data` should be at `...38`, not `...2c`.
How could CPU 1 be writing to `...2c`? If `blk` is at `...28`, its data *would* be at `...2c`. Then, writing 7 bytes writes to `...2c` to `...32`, overlapping with the read at `...30`.
The write happens with `vsnprintf`. `vsnprintf` writes to `buf`. In `vsnprintf`, `buf` is the same as `text`, so if the write is at `...2c`, `text` would need to be at `...2c`. But isn't the problem that `vsnprintf` should be writing to `...30`?
If `text` *is* at `...2c`, and `vsnprintf` is called with the proper sizes, it writes to the correct memory location, but then `blk->data` *is* at `...2c`! Then, `blk` should be at `...24`. If block A is at `...24`, its data at `...2c`.
If block B, that is being read, is at
|
| 67/2 |
2026/05/20 00:15 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:kernel/printk/printk_ringbuffer.c IncludeLines:true Name:get_next_lpos]
Results: map[SourceCode:1030: /* Determine the end of a data block. */
1031: static unsigned long get_next_lpos(struct prb_data_ring *data_ring,
1032: unsigned long lpos, unsigned int size)
1033: {
1034: unsigned long begin_lpos;
1035: unsigned long next_lpos;
1036:
1037: begin_lpos = lpos;
1038: next_lpos = lpos + size;
1039:
1040: /* First check if the data block does not wrap. */
1041: if (!is_blk_wrapped(data_ring, begin_lpos, next_lpos))
1042: return next_lpos;
1043:
1044: /* Wrapping data blocks store their data at the beginning. */
1045: return (DATA_THIS_WRAP_START_LPOS(data_ring, next_lpos) + size);
1046: }
SourceFile:kernel/printk/printk_ringbuffer.c]
|
| 68/2 |
2026/05/20 00:15 |
llm |
expert |
1m
Model:
Tokens:
input: 74315
output: 66
thoughts: 15424
Thoughts: **Analysis of a Kernel Data Race in the Printk Ringbuffer**
Okay, so I've been dissecting this KCSAN report, and it looks like we've got a classic race condition in the kernel's printk ringbuffer. I see that `get_next_lpos` is simply adding the `size`, and because `to_blk_size` returns multiples of 8, the next logical position (`next_lpos`) is always a multiple of 8 if the current position (`lpos`) is. Since we start at zero, we're always dealing with 8-byte aligned addresses. This means the block addresses (`blk`) and their data (`blk->data`) are always at multiples of 8.
I see a write to `0xffffffff8936612c` is being flagged, which isn't a multiple of 8 (it ends in `c` which is a multiple of 4, but not 8), but the buffer (`text`) *is* aligned to 8! So, the key must be an offset. This is it: `vsnprintf` is writing the string piece by piece. The buffer `buf` is `text + offset`. So the write is happening relative to the 8-byte aligned `text` pointer.
Now, this looks like `vsnprintf` is writing to an *offset* of a buffer! I see, `buf = text + 4`, `vsnprintf` is writing the string piece by piece! Let's say `vsnprintf` with format string `" %s %s %s%s: %pV"`. It has these parts: `dev_driver_string`, `dev_name`, `netdev_name`, `netdev_reg_state`, and `%pV`.
If the prefix (the first part) is 4 bytes long, then the write to `%pV` is going to `text + 4`. The inner `vsnprintf` writes "type 2 " (7 bytes) at the offset 4. `data_make_reusable` reads `blk->id` at `...30`, so it's a concurrent read, and the race.
So, if `text` is `...28`, and the prefix is 4, `%pV` then writes to `...2c` to `...32`. Block A would end at `...38` if the size is 24 and at `...30` if the size is 16. Then, if the write goes to `...32` it is *past* the end of Block A. So, the read *must* overlap, or there must be a write-past-end condition.
Now, the size is calculated through `reserve_size`. I see that `to_blk_size(12)` results in 24 (or `ALIGN(8 + 12, 8)`). If `reserve_size` is calculated small at 12 bytes. If the actual string turns out to be bigger! Then this will create the overflow!
So, the issue is, the size calculation can be off because of the values returned by `dev_driver_string`, `dev_name` and `netdev_reg_state`.
I keep coming back to this: Why is it *always* writing the 7 bytes, and that's the key.
This must mean that `reserve_size` is smaller than the actual string length. So the blocks are allocated small. If reserve size is 12 bytes and the string is 11, then the blocks are made small, size 16. So the data race occurs. The overlapping happens as the `vsnprintf` writes its 7 bytes.
I see that `vsnprintf` can be bounded by a calculated `size`.
The key is if the string is longer than the size argument, the `end - str` becomes small and `memcpy` doesn't write. The string is *truncated*!
Ah, I see it! KCSAN is *intercepting* the `memcpy`! So it's not a real write of a larger amount. So the check `str < end` in `vsnprintf` must *not* be hit. The write has to be shorter than `end - str`. Otherwise, the write doesn't *happen*. So the bug is in the size, not a real out of bounds condition.
What size argument is passed to `vsnprintf`? It's `reserve_size`. This *is* the size limit! The total size written to that block cannot *exceed* it! So, the race is *not* a real out-of-bounds write
|
| 69/2 |
2026/05/20 00:17 |
tool |
set-results |
0m
Args: map[DenialOfService:false Exploitable:false FilesystemTrigger:false NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
Results: map[DenialOfService:false Exploitable:false FilesystemTrigger:false NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
|
| 70/2 |
2026/05/20 00:17 |
llm |
expert |
0m
Model:
Tokens:
input: 90894
output: 662
thoughts: 631
Thoughts: **My Analysis of the KCSAN-Detected Data Race in the Printk Ringbuffer**
Okay, the results are in. Time to synthesize this into the final response.
Essentially, KCSAN flagged a data race within the printk ringbuffer, specifically in `kernel/printk/printk_ringbuffer.c`. I see the race occurring between `vsnprintf`, which is writing log messages, and `data_make_reusable`, which is trying to reclaim space in the ringbuffer. Let me break it down:
* **Writer's Perspective:** CPU 1, formatting a log messageβin this case from `nsim_udp_tunnel_unset_port` and using `netdev_info`βis directly writing to a new block within the printk ringbuffer. This is done with `vsnprintf`, which uses `memcpy` for literal strings.
* **Reader's Perspective:** Meanwhile, CPU 0 is working to make space by advancing the tail of the ringbuffer. It reads the block `id` (`id = blk->id;`) of the oldest block to determine if it can be recycled.
The key is that the printk ringbuffer is a lockless data structure. It's meant to be fast, but that means it avoids locks. When a new block is allocated, it can potentially overwrite memory previously used by an old block. Here's where the race becomes clear: if CPU 0 reads the `id` of an old block *after* CPU 1 has already updated the tail and started writing into that block, CPU 0 will, effectively, read garbageβit'll be reading parts of the new string CPU 1 is in the process of writing.
Fortunately, this is a *known* and *intended* aspect of the lockless design. The code in `data_make_reusable` anticipates it explicitly, as seen in the code comments. It understands that reading an inconsistent `id` is possible due to the concurrent write and the comments acknowledge the data race. The logic within `data_make_reusable` contains a check to make sure the data area has not been re-purposed. If the `id` is corrupt, the validation will fail (e.g., the ID doesn't match the descriptor, or the logical position is wrong). Consequently, it will return `false`, update and re-read, avoiding an issue.
The crucial point here is that `vsnprintf` is bound by the size of the allocated block. Because of this, it can't lead to out-of-bounds memory corruption. This race is only a read of a concurrently modified value. The lockless design handles this gracefully, and the invalid read is discarded.
Therefore, this isn't a security vulnerability. This cannot be exploited for privilege escalation, memory corruption, or even denial of service, as the mechanism correctly resolves the conflicting reads. It is a known characteristic of the design.
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Results: map[Explanation:Based on the analysis of the stack traces and the source code, this is a
**benign data race** in the kernel's lockless printk ringbuffer. It has no
security impact.
### Root Cause Analysis
The KCSAN report highlights a data race between a writer (`vsnprintf`) and a
reader (`data_make_reusable`):
1. **Writer (CPU 1)**: A task is printing a network device log message
(`netdev_info` from `nsim_udp_tunnel_unset_port`). The printk subsystem
allocates a new block in the ringbuffer and uses `vsnprintf` to format the
string directly into this block's data section (`blk->data`).
2. **Reader (CPU 0)**: Another task is concurrently trying to allocate space in
the ringbuffer (triggered by an ext4 mount failure message). To free up space,
it calls `data_push_tail`, which iterates over old blocks via
`data_make_reusable`. It reads the block ID (`id = blk->id;`) of the oldest
block to check if it can be recycled.
Because the ringbuffer is a lockless circular buffer, newly allocated blocks
wrap around and overwrite old blocks. If CPU 0 reads the `id` of an old block
*after* CPU 1 has already pushed the tail and started writing its new string
over that exact memory location, CPU 0 will read bytes of the new string (e.g.,
the string `"type 2 "`) instead of a valid block ID.
This race is **intentional and safely handled** by the lockless algorithm. The
source code in `data_make_reusable` explicitly documents this exact scenario:
```c
/*
* Load the block ID from the data block. This is a data race
* against a writer that may have newly reserved this data
* area. If the loaded value matches a valid descriptor ID,
* the blk_lpos of that descriptor will be checked to make
* sure it points back to this data block. If the check fails,
* the data area has been recycled by another writer.
*/
id = blk->id; /* LMM(data_make_reusable:A) */
```
When `data_make_reusable` reads the garbage ID, it passes it to `desc_read()`.
The validation will fail (either the ID won't match the descriptor's state, or
the logical position won't match), causing it to safely abort, re-read the newly
updated tail position, and continue correctly.
### Security Impact
- **Exploitable / Memory Corruption**: **No**. `vsnprintf` is strictly bounded
by the allocated block size (`reserve_size`), so it cannot write out-of-bounds.
The reader safely discards the torn/garbage read.
- **Denial of Service**: **No**. The lockless algorithm handles the race
gracefully without crashing or hanging.
- **Triggerability**: While any unprivileged user can trigger concurrent
`printk` calls, the resulting data race is completely benign and does not affect
system stability or security.]
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