KASAN: slab-use-after-free Read in seq_printf

Status: premoderation: reported C repro on 2026/09/23 06:02
Bug presence: origin:lts
[Documentation on labels]
Reported-by: syzbot+2639b0a8b6a0d6cf6d3e@syzkaller.appspotmail.com
First crash: 49d, last: 5h44m
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/10/12 lts (merge base) e9f803bf2b03 C [report] KASAN: slab-use-after-free Read in seq_printf
2026/10/12 upstream (ToT) 24a19b953e2a C Didn't crash
▶ ▼ Similar bugs (15)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-out-of-bounds Read in seq_printf fs 19 5 549d 654d 0/29 auto-obsoleted due to no activity on 2025/08/09 17:54
upstream KASAN: slab-use-after-free Read in seq_printf prio:high fs 19 C error 91 13d 53d 0/29 upstream: reported C repro on 2026/09/19 02:15
linux-6.6 KASAN: slab-use-after-free Read in seq_printf 19 2 29d 78d 0/2 upstream: reported on 2026/08/25 13:48
android-5-15 KASAN: use-after-free Read in seq_printf (2) 19 syz, C 24 1d10h 30d 0/2 upstream: reported C repro on 2026/10/12 05:38
linux-6.1 KASAN: use-after-free Read in seq_printf 19 3 19d 19d 0/3 upstream: reported on 2026/10/23 08:35
upstream KMSAN: uninit-value in seq_printf (2) fs 7 syz, C 99 1610d 1876d 0/29 auto-closed as invalid on 2022/09/30 02:43
linux-5.15 KASAN: use-after-free Read in seq_printf 19 4 10d 49d 0/3 upstream: reported on 2026/09/23 14:29
android-6-1 KASAN: slab-out-of-bounds Read in seq_printf (2) 17 1 221d 221d 0/2 auto-obsoleted due to no activity on 2026/07/03 17:29
android-5-10 KASAN: use-after-free Read in seq_printf (3) 19 syz, C 64 20h20m 30d 0/2 upstream: reported C repro on 2026/10/12 19:47
android-5-10 KASAN: use-after-free Read in seq_printf 19 15 413d 521d 0/2 auto-obsoleted due to no activity on 2025/12/23 06:43
upstream KMSAN: kernel-infoleak in __skb_datagram_iter net 9 68 1142d 1247d 23/29 fixed on 2023/09/28 17:51
android-6-1 KASAN: slab-out-of-bounds Read in seq_printf 19 2 417d 422d 0/2 auto-obsoleted due to no activity on 2025/12/19 00:57
android-5-10 KASAN: use-after-free Read in seq_printf (2) 19 1 301d 301d 0/2 auto-obsoleted due to no activity on 2026/04/14 16:00
android-6-1 KASAN: use-after-free Read in seq_printf origin:lts 19 syz, C 26 3d13h 48d 0/2 upstream: reported C repro on 2026/09/24 21:21
android-5-15 KASAN: use-after-free Read in seq_printf 19 1 419d 419d 0/2 auto-obsoleted due to no activity on 2025/12/17 23:30

Sample crash report:
printk: legacy console [ttyS0] enabled
==================================================================
BUG: KASAN: slab-use-after-free in string_nocheck lib/vsprintf.c:646 [inline]
BUG: KASAN: slab-use-after-free in string+0x20f/0x2b0 lib/vsprintf.c:728
Read of size 1 at addr ffff8881056a28e0 by task syz-executor668/312

CPU: 0 UID: 0 PID: 312 Comm: syz-executor668 Not tainted syzkaller #0 1736d3b6ee88961c9d73e511fbf4428dbce80e3d
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x140/0x1c0 lib/dump_stack.c:120
 print_address_description+0x71/0x210 mm/kasan/report.c:377
 print_report+0x4a/0x70 mm/kasan/report.c:481
 kasan_report+0x162/0x1a0 mm/kasan/report.c:594
 __asan_report_load1_noabort+0x18/0x20 mm/kasan/report_generic.c:378
 string_nocheck lib/vsprintf.c:646 [inline]
 string+0x20f/0x2b0 lib/vsprintf.c:728
 vsnprintf+0xe65/0x1ad0 lib/vsprintf.c:2803
 seq_vprintf fs/seq_file.c:391 [inline]
 seq_printf+0x189/0x290 fs/seq_file.c:406
 show_interrupts+0x6d2/0x7f0 kernel/irq/proc.c:524
 traverse+0x21e/0x700 fs/seq_file.c:111
 seq_read_iter+0xdbd/0xf30 fs/seq_file.c:195
 proc_reg_read_iter+0x1ea/0x2c0 fs/proc/inode.c:299
 do_iter_readv_writev+0x62c/0x820 fs/read_write.c:-1
 vfs_readv+0x301/0xa00 fs/read_write.c:1037
 do_preadv fs/read_write.c:1154 [inline]
 __do_sys_preadv fs/read_write.c:1204 [inline]
 __se_sys_preadv fs/read_write.c:1199 [inline]
 __x64_sys_preadv+0x19f/0x2c0 fs/read_write.c:1199
 x64_sys_call+0x1ee9/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:296
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f2ffea6bdf9
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd49dfc6e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 636f7270796d2f2e RCX: 00007f2ffea6bdf9
RDX: 0000000000000001 RSI: 0000200000000880 RDI: 0000000000000006
RBP: 0000000000000001 R08: 0000000000000004 R09: 00007ffd49dfc818
R10: 0000000000000200 R11: 0000000000000246 R12: 00007ffd49dfc808
R13: 0000000000000002 R14: 00007f2ffeafcca0 R15: 0000000000000002
 </TASK>

Allocated by task 1:
 kasan_save_stack mm/kasan/common.c:49 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:70
 kasan_save_alloc_info+0x3a/0x50 mm/kasan/generic.c:565
 poison_kmalloc_redzone mm/kasan/common.c:379 [inline]
 __kasan_kmalloc+0x96/0xb0 mm/kasan/common.c:396
 kasan_kmalloc include/linux/kasan.h:261 [inline]
 __do_kmalloc_node mm/slub.c:4397 [inline]
 __kmalloc_node_track_caller_noprof+0x24e/0x4f0 mm/slub.c:4416
 kvasprintf+0xf1/0x260 lib/kasprintf.c:25
 kasprintf+0xe3/0x140 lib/kasprintf.c:59
 serial_core_add_one_port drivers/tty/serial/serial_core.c:3171 [inline]
 serial_core_register_port+0x83b/0x23c0 drivers/tty/serial/serial_core.c:3414
 serial_ctrl_register_port+0x21/0x30 drivers/tty/serial/serial_ctrl.c:41
 uart_add_one_port+0x21/0x30 drivers/tty/serial/serial_port.c:143
 serial8250_register_8250_port+0x17ab/0x21d0 drivers/tty/serial/8250/8250_core.c:823
 serial_pnp_probe+0x54b/0x750 drivers/tty/serial/8250/8250_pnp.c:490
 pnp_device_probe+0x316/0x4e0 drivers/pnp/driver.c:111
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x2e1/0x8b0 drivers/base/dd.c:657
 __driver_probe_device+0x193/0x280 drivers/base/dd.c:799
 driver_probe_device+0x54/0x3f0 drivers/base/dd.c:829
 __driver_attach+0x422/0x5e0 drivers/base/dd.c:1215
 bus_for_each_dev+0x249/0x2d0 drivers/base/bus.c:370
 driver_attach+0x46/0x50 drivers/base/dd.c:1233
 bus_add_driver+0x393/0x730 drivers/base/bus.c:682
 driver_register+0x2b7/0x3c0 drivers/base/driver.c:246
 pnp_register_driver+0x81/0x90 drivers/pnp/driver.c:280
 serial8250_pnp_init+0x19/0x20 drivers/tty/serial/8250/8250_pnp.c:540
 serial8250_init+0xcc/0x1d0 drivers/tty/serial/8250/8250_platform.c:324
 do_one_initcall+0x1e8/0x6a0 init/main.c:1406
 do_initcall_level+0x174/0x2e5 init/main.c:1468
 do_initcalls+0x7e/0x160 init/main.c:1484
 do_basic_setup+0x95/0xb0 init/main.c:1503
 kernel_init_freeable+0x2b1/0x400 init/main.c:1717
 kernel_init+0x21/0x1e0 init/main.c:1606
 ret_from_fork+0x64/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Freed by task 312:
 kasan_save_stack mm/kasan/common.c:49 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:70
 kasan_save_free_info+0x44/0x50 mm/kasan/generic.c:579
 poison_slab_object mm/kasan/common.c:249 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:266
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2445 [inline]
 slab_free mm/slub.c:4716 [inline]
 kfree+0x158/0x440 mm/slub.c:4877
 serial_core_remove_one_port drivers/tty/serial/serial_core.c:3273 [inline]
 serial_core_unregister_port+0x469/0xa50 drivers/tty/serial/serial_core.c:3449
 serial_ctrl_unregister_port+0x21/0x30 drivers/tty/serial/serial_ctrl.c:46
 uart_remove_one_port+0x21/0x30 drivers/tty/serial/serial_port.c:149
 serial8250_unregister_port+0x1cc/0x6b0 drivers/tty/serial/8250/8250_core.c:886
 serial_pnp_remove+0x5d/0xa0 drivers/tty/serial/8250/8250_pnp.c:507
 pnp_device_remove+0x8d/0x270 drivers/pnp/driver.c:133
 device_remove drivers/base/dd.c:567 [inline]
 __device_release_driver drivers/base/dd.c:1272 [inline]
 device_release_driver_internal+0x4ad/0x830 drivers/base/dd.c:1295
 device_driver_detach+0x3f/0x50 drivers/base/dd.c:1331
 unbind_store+0x1ab/0x1f0 drivers/base/bus.c:244
 drv_attr_store+0x91/0xb0 drivers/base/bus.c:125
 sysfs_kf_write+0x13e/0x160 fs/sysfs/file.c:136
 kernfs_fop_write_iter+0x319/0x510 fs/kernfs/file.c:352
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x75f/0xfd0 fs/read_write.c:684
 ksys_write+0x145/0x260 fs/read_write.c:737
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x7f/0x90 fs/read_write.c:746
 x64_sys_call+0x271c/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:47 [inline]
 do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

The buggy address belongs to the object at ffff8881056a28e0
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes inside of
 freed 8-byte region [ffff8881056a28e0, ffff8881056a28e8)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1056a2
anon flags: 0x4000000000000000(zone=1)
page_type: f5(slab)
raw: 4000000000000000 ffff888100041500 0000000000000000 0000000000000001
raw: 0000000000000000 0000000080800080 00000001f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid 1 (swapper/0), ts 3011079691, free_ts 0
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook+0x37d/0x3b0 mm/page_alloc.c:1864
 prep_new_page+0x2d/0x180 mm/page_alloc.c:1872
 get_page_from_freelist+0x4aea/0x4ba0 mm/page_alloc.c:3949
 __alloc_pages_noprof+0x35a/0x7e0 mm/page_alloc.c:5316
 alloc_slab_page+0x6b/0x1e0 mm/slub.c:-1
 allocate_slab+0x69/0x430 mm/slub.c:2687
 new_slab mm/slub.c:2741 [inline]
 ___slab_alloc+0x591/0x8c0 mm/slub.c:3934
 __slab_alloc mm/slub.c:4025 [inline]
 __slab_alloc_node mm/slub.c:4078 [inline]
 slab_alloc_node mm/slub.c:4241 [inline]
 __do_kmalloc_node mm/slub.c:4396 [inline]
 __kmalloc_noprof+0x2fc/0x510 mm/slub.c:4409
 kmalloc_noprof include/linux/slab.h:886 [inline]
 acpi_ex_allocate_name_string+0xed/0x420 drivers/acpi/acpica/exnames.c:66
 acpi_ex_get_name_string+0x2a7/0x490 drivers/acpi/acpica/exnames.c:367
 acpi_ds_create_operand+0x16c/0x8c0 drivers/acpi/acpica/dsutils.c:446
 acpi_ds_create_operands+0x275/0x420 drivers/acpi/acpica/dsutils.c:707
 acpi_ds_eval_buffer_field_operands+0x6b/0x320 drivers/acpi/acpica/dsopcode.c:290
 acpi_ds_exec_end_op+0x9de/0x1210 drivers/acpi/acpica/dswexec.c:548
 acpi_ps_parse_loop+0xc83/0x1ac0 drivers/acpi/acpica/psloop.c:525
 acpi_ps_parse_aml+0x218/0x9b0 drivers/acpi/acpica/psparse.c:475
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8881056a2780: 00 fc fc fc 05 fc fc fc 00 fc fc fc 06 fc fc fc
 ffff8881056a2800: fa fc fc fc 02 fc fc fc 06 fc fc fc 00 fc fc fc
>ffff8881056a2880: fa fc fc fc 07 fc fc fc 00 fc fc fc fa fc fc fc
                                                       ^
 ffff8881056a2900: 00 fc fc fc fa fc fc fc 07 fc fc fc fa fc fc fc
 ffff8881056a2980: 00 fc fc fc 07 fc fc fc fa fc fc fc fa fc fc fc
===================================

Crashes (24):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/11/01 02:54 android16-6.12 abad7aaa7f9f 25a0ae84 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/19 12:46 android16-6.12 49f96790cc76 432c0077 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/05 15:28 android16-6.12 3a7d1771d492 af63e995 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/11/11 18:01 android16-6.12 153de33f91d6 e56a968c .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/30 21:16 android16-6.12 21e8b8d58095 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/19 12:10 android16-6.12 49f96790cc76 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/19 11:49 android16-6.12 49f96790cc76 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/18 21:48 android16-6.12 49f96790cc76 432c0077 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/16 13:44 android16-6.12 0a5243953af0 4c840a2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/15 08:33 android16-6.12 4fc23344fdfc 8fb0ae89 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/14 19:53 android16-6.12 9dd8cf331e61 1a71827b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/13 18:56 android16-6.12 3f843d670131 5a1eeac4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/13 12:15 android16-6.12 3f843d670131 5a1eeac4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/12 22:47 android16-6.12 602cc832d2b7 745a967f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/12 14:13 android16-6.12 c82b35cb007f 745a967f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/04 12:49 android16-6.12 3a7d1771d492 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/02 18:31 android16-6.12 3a7d1771d492 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/10/01 19:05 android16-6.12 f82d63769e69 f5cdae2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/09/29 12:04 android16-6.12 da245f6c05a1 7bf4ea23 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/09/29 11:34 android16-6.12 da245f6c05a1 7bf4ea23 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/09/29 02:46 android16-6.12 da245f6c05a1 7bf4ea23 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/09/25 07:02 android16-6.12 558b94a8d268 f281d9d2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/09/25 01:53 android16-6.12 558b94a8d268 3c3cdf19 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
2026/09/23 06:01 android16-6.12 c8909f7cf138 5207b90e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust KASAN: slab-use-after-free Read in seq_printf
* Struck through repros no longer work on HEAD.