syzbot
KASAN: slab-use-after-free Read in v4l2_release (3)
Status:
upstream: reported C repro on 2026/09/11 16:15
Subsystems:
media
Labels:
prio:high
[Documentation on labels]
Reported-by: syzbot+34957180b0ed2581edaf@syzkaller.appspotmail.com
First crash: 55d, last: 1d04h
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Last patch testing requests (6)
Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in v4l2_release+0xb5/0x350 drivers/media/v4l2-core/v4l2-dev.c:466
Read of size 8 at addr ffff888027306658 by task syz-executor151/5968
CPU: 1 UID: 0 PID: 5968 Comm: syz-executor151 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description+0x55/0x1e0 mm/kasan/report.c:378
print_report+0x58/0x70 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
v4l2_release+0xb5/0x350 drivers/media/v4l2-core/v4l2-dev.c:466
__fput+0x408/0xa40 fs/file_table.c:512
fput_close_sync+0x11f/0x240 fs/file_table.c:618
filp_close_sync fs/open.c:1573 [inline]
__do_sys_close fs/open.c:1596 [inline]
__se_sys_close+0xa2/0x160 fs/open.c:1583
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline]
do_int80_emulation+0x198/0x500 arch/x86/entry/syscall_32.c:166
asm_int80_emulation+0x1a/0x20 arch/x86/include/asm/idtentry.h:598
RIP: 0023:0xf7ef68db
Code: 57 56 53 8b 44 24 14 f6 00 08 75 23 8b 44 24 18 8b 5c 24 1c 8b 4c 24 20 8b 54 24 24 8b 74 24 28 8b 7c 24 2c 8b 6c 24 30 cd 80 <5b> 5e 5f 5d c3 5b 5e 5f 5d e9 d7 e8 ff ff 66 90 66 90 66 90 90 55
RSP: 002b:00000000ffee1e5c EFLAGS: 00000246 ORIG_RAX: 0000000000000006
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Allocated by task 5757:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:409 [inline]
__kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:426
kasan_kmalloc include/linux/kasan.h:263 [inline]
__kmalloc_cache_noprof+0x31c/0x600 mm/slub.c:5680
_kmalloc_noprof include/linux/slab.h:991 [inline]
_kzalloc_noprof include/linux/slab.h:1312 [inline]
sur40_probe+0x16c/0xfa0 drivers/input/touchscreen/sur40.c:675
usb_probe_interface+0x751/0xe00 drivers/usb/core/driver.c:399
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x254/0xae0 drivers/base/dd.c:707
__driver_probe_device+0x1e8/0x360 drivers/base/dd.c:869
driver_probe_device+0x4f/0x240 drivers/base/dd.c:899
__device_attach_driver+0x270/0x410 drivers/base/dd.c:1027
bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:500
__device_attach+0x2bd/0x430 drivers/base/dd.c:1131
device_initial_probe+0x9c/0x100 drivers/base/dd.c:1190
__bus_probe_device+0x126/0x220 drivers/base/bus.c:614
device_add+0x7d7/0xb80 drivers/base/core.c:3778
usb_set_configuration+0x1bb5/0x2260 drivers/usb/core/message.c:2280
usb_generic_driver_probe+0x8d/0x150 drivers/usb/core/generic.c:250
usb_probe_device+0x1c3/0x3b0 drivers/usb/core/driver.c:293
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x254/0xae0 drivers/base/dd.c:707
__driver_probe_device+0x1e8/0x360 drivers/base/dd.c:869
driver_probe_device+0x4f/0x240 drivers/base/dd.c:899
__device_attach_driver+0x270/0x410 drivers/base/dd.c:1027
bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:500
__device_attach+0x2bd/0x430 drivers/base/dd.c:1131
device_initial_probe+0x9c/0x100 drivers/base/dd.c:1190
__bus_probe_device+0x126/0x220 drivers/base/bus.c:614
device_add+0x7d7/0xb80 drivers/base/core.c:3778
usb_new_device+0x9aa/0x1690 drivers/usb/core/hub.c:2713
hub_port_connect drivers/usb/core/hub.c:5585 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5725 [inline]
port_event drivers/usb/core/hub.c:5889 [inline]
hub_event+0x28e8/0x4d30 drivers/usb/core/hub.c:5971
process_one_work kernel/workqueue.c:3495 [inline]
process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Freed by task 5968:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:264 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:296
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2780 [inline]
slab_free mm/slub.c:6630 [inline]
kfree+0x1c5/0x650 mm/slub.c:6923
sur40_disconnect+0xaf/0x140 drivers/input/touchscreen/sur40.c:835
usb_unbind_interface+0x295/0x9c0 drivers/usb/core/driver.c:460
device_remove drivers/base/dd.c:619 [inline]
__device_release_driver drivers/base/dd.c:1357 [inline]
device_release_driver_internal+0x48d/0x7d0 drivers/base/dd.c:1380
unbind_store+0x1a1/0x1d0 drivers/base/bus.c:244
kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x612/0xba0 fs/read_write.c:687
ksys_write+0x150/0x270 fs/read_write.c:739
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline]
do_int80_emulation+0x198/0x500 arch/x86/entry/syscall_32.c:166
asm_int80_emulation+0x1a/0x20 arch/x86/include/asm/idtentry.h:598
The buggy address belongs to the object at ffff888027306000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 1624 bytes inside of
freed 4096-byte region [ffff888027306000, ffff888027307000)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27300
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88813ff29140 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813ff29140 dead000000000100 dead000000000122
head: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 5706504568
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1856
prep_new_page mm/page_alloc.c:1864 [inline]
get_page_from_freelist+0x220f/0x2280 mm/page_alloc.c:3935
__alloc_frozen_pages_noprof+0x1fe/0x410 mm/page_alloc.c:5444
alloc_slab_page mm/slub.c:3384 [inline]
allocate_slab+0x7d/0x5e0 mm/slub.c:3499
new_slab mm/slub.c:3550 [inline]
refill_objects+0x2d5/0x350 mm/slub.c:7539
refill_sheaf mm/slub.c:2917 [inline]
__pcs_replace_empty_main+0x2c8/0x6c0 mm/slub.c:4811
alloc_from_pcs mm/slub.c:4887 [inline]
slab_alloc_node mm/slub.c:5021 [inline]
__kmalloc_cache_noprof+0x396/0x600 mm/slub.c:5676
_kmalloc_noprof include/linux/slab.h:991 [inline]
_kzalloc_noprof include/linux/slab.h:1312 [inline]
kobject_uevent_env+0x289/0x9e0 lib/kobject_uevent.c:543
driver_register+0x2d4/0x320 drivers/base/driver.c:182
panel_edp_init+0x1d/0x60 drivers/gpu/drm/panel/panel-edp.c:2320
do_one_initcall+0x250/0x870 init/main.c:1419
do_initcall_level+0x10a/0x1a0 init/main.c:1481
do_initcalls+0x59/0xa0 init/main.c:1497
kernel_init_freeable+0x29d/0x3e0 init/main.c:1732
kernel_init+0x22/0x1d0 init/main.c:1622
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
page_owner free stack trace missing
Memory state around the buggy address:
ffff888027306500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888027306580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888027306600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888027306680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888027306700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
----------------
Code disassembly (best guess):
0: 57 push %rdi
1: 56 push %rsi
2: 53 push %rbx
3: 8b 44 24 14 mov 0x14(%rsp),%eax
7: f6 00 08 testb $0x8,(%rax)
a: 75 23 jne 0x2f
c: 8b 44 24 18 mov 0x18(%rsp),%eax
10: 8b 5c 24 1c mov 0x1c(%rsp),%ebx
14: 8b 4c 24 20 mov 0x20(%rsp),%ecx
18: 8b 54 24 24 mov 0x24(%rsp),%edx
1c: 8b 74 24 28 mov 0x28(%rsp),%esi
20: 8b 7c 24 2c mov 0x2c(%rsp),%edi
24: 8b 6c 24 30 mov 0x30(%rsp),%ebp
28: cd 80 int $0x80
* 2a: 5b pop %rbx <-- trapping instruction
2b: 5e pop %rsi
2c: 5f pop %rdi
2d: 5d pop %rbp
2e: c3 ret
2f: 5b pop %rbx
30: 5e pop %rsi
31: 5f pop %rdi
32: 5d pop %rbp
33: e9 d7 e8 ff ff jmp 0xffffe90f
38: 66 90 xchg %ax,%ax
3a: 66 90 xchg %ax,%ax
3c: 66 90 xchg %ax,%ax
3e: 90 nop
3f: 55 push %rbp
Struck through repros no longer work on HEAD.