[syzbot] [media?] [usb?] kernel BUG in v4l2_device_put

[syzbot] [media?] [usb?] kernel BUG in v4l2_device_put

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    8f7df005a756 Add linux-next specific files for 20261020
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1061bb05580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9c1b9b13e3e4ce1a
dashboard link: https://syzkaller.appspot.com/bug?extid=809dfc586f33fc44b6ac
compiler:       Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1104258e580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=176a5481580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4ecf38da9706/disk-8f7df005.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/feab027e2efe/vmlinux-8f7df005.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ded91a573e5a/bzImage-8f7df005.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+809dfc586f33fc44b6ac@syzkaller.appspotmail.com

refcount_t: underflow; use-after-free.
------------[ cut here ]------------
kernel BUG at lib/refcount.c:37!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 7562 Comm: v4l_id Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
RIP: 0010:refcount_warn_saturate+0x104/0x110 lib/refcount.c:37
Code: 5d ff ff ff e8 4d c1 d1 fc 48 c7 c7 00 e3 8d 8c e8 61 69 30 fc 90 0f 0b e8 39 c1 d1 fc 48 c7 c7 80 e3 8d 8c e8 4d 69 30 fc 90 <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc900065b7cc0 EFLAGS: 00010246
RAX: 0000000000000026 RBX: 0000000000000003 RCX: 86d7792bd9d84300
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff90033f40
RBP: 0000000000000000 R08: ffffffff81a6b7f0 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff237c1d8 R12: 1ffffffff1973318
R13: dffffc0000000000 R14: ffff88807cc000b0 R15: ffffffff882fcb70
FS:  00007f2b1fb76880(0000) GS:ffff8881234da000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055aef7b1964d CR3: 0000000075e40000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __refcount_sub_and_test include/linux/refcount.h:400 [inline]
 __refcount_dec_and_test include/linux/refcount.h:432 [inline]
 refcount_dec_and_test include/linux/refcount.h:450 [inline]
 kref_put include/linux/kref.h:64 [inline]
 v4l2_device_put+0xc2/0xd0 drivers/media/v4l2-core/v4l2-device.c:56
 device_release+0xc4/0x1f0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x222/0x550 lib/kobject.c:737
 video_put drivers/media/v4l2-core/v4l2-dev.c:173 [inline]
 v4l2_release+0x273/0x350 drivers/media/v4l2-core/v4l2-dev.c:480
 __fput+0x408/0xa40 fs/file_table.c:513
 fput_close_sync+0x11f/0x240 fs/file_table.c:619
 filp_close_sync fs/open.c:1897 [inline]
 __do_sys_close fs/open.c:2153 [inline]
 __se_sys_close+0xa2/0x160 fs/open.c:2140
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2b1f4a7407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007fffdbbfc440 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 00007f2b1fb76880 RCX: 00007f2b1f4a7407
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f2b1fb766e8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000013
R13: 00007fffdbbfc670 R14: 00007f2b1fcdd000 R15: 000055aef7b1d4d8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:refcount_warn_saturate+0x104/0x110 lib/refcount.c:37
Code: 5d ff ff ff e8 4d c1 d1 fc 48 c7 c7 00 e3 8d 8c e8 61 69 30 fc 90 0f 0b e8 39 c1 d1 fc 48 c7 c7 80 e3 8d 8c e8 4d 69 30 fc 90 <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc900065b7cc0 EFLAGS: 00010246
RAX: 0000000000000026 RBX: 0000000000000003 RCX: 86d7792bd9d84300
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff90033f40
RBP: 0000000000000000 R08: ffffffff81a6b7f0 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff237c1d8 R12: 1ffffffff1973318
R13: dffffc0000000000 R14: ffff88807cc000b0 R15: ffffffff882fcb70
FS:  00007f2b1fb76880(0000) GS:ffff8881234da000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055aef7b1964d CR3: 0000000075e40000 CR4: 00000000003526f0


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup