[syzbot] [media?] WARNING in vidtv_start_feed

[syzbot <syzbot+525fda837bd5fc2be560@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    4e69c1856bfd Merge tag 'drm-next-2026-08-20' of https://gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12a60625580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6330e13b2e20bb12
dashboard link: https://syzkaller.appspot.com/bug?extid=525fda837bd5fc2be560
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f9abc0d6723c/disk-4e69c185.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/11f2728e2c65/vmlinux-4e69c185.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a175945b1e38/bzImage-4e69c185.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+525fda837bd5fc2be560@syzkaller.appspotmail.com

------------[ cut here ]------------
DEBUG_LOCKS_WARN_ON(lock->magic != lock)
WARNING: kernel/locking/mutex.c:625 at __mutex_lock_common kernel/locking/mutex.c:625 [inline], CPU#1: syz.0.342/7078
WARNING: kernel/locking/mutex.c:625 at __mutex_lock+0x12e6/0x1550 kernel/locking/mutex.c:821, CPU#1: syz.0.342/7078
Modules linked in:
CPU: 1 UID: 0 PID: 7078 Comm: syz.0.342 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:__mutex_lock_common kernel/locking/mutex.c:625 [inline]
RIP: 0010:__mutex_lock+0x12ed/0x1550 kernel/locking/mutex.c:821
Code: 29 79 90 48 c1 e8 03 0f b6 04 18 84 c0 0f 85 47 02 00 00 83 3d 77 a5 9a 04 00 75 13 48 8d 3d ba 9b 9d 04 48 c7 c6 80 fe 0c 8c <67> 48 0f b9 3a 90 e9 67 ee ff ff 90 0f 0b 90 e9 3a f2 ff ff 90 0f
RSP: 0018:ffffc900051b7960 EFLAGS: 00010246
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: 0000000000080000
RDX: ffffc9001174a000 RSI: ffffffff8c0cfe80 RDI: ffffffff907c1f80
RBP: ffffc900051b7af0 R08: ffffffff90792933 R09: 1ffffffff20f2526
R10: dffffc0000000000 R11: fffffbfff20f2527 R12: ffff888026075128
R13: 0000000000000000 R14: 1ffff92000a36f40 R15: 0000000000000000
FS:  00007fad388b86c0(0000) GS:ffff888124e0c000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b33316ff8 CR3: 000000002e6c2000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 vidtv_start_feed+0x102/0x5a0 drivers/media/test-drivers/vidtv/vidtv_bridge.c:233
 dmx_ts_feed_start_filtering+0x129/0x220 drivers/media/dvb-core/dvb_demux.c:747
 dvb_dmxdev_start_feed drivers/media/dvb-core/dmxdev.c:658 [inline]
 dvb_dmxdev_filter_start+0x434/0x10d0 drivers/media/dvb-core/dmxdev.c:769
 dvb_demux_do_ioctl+0x48b/0x540 drivers/media/dvb-core/dmxdev.c:1099
 dvb_usercopy+0x199/0x2e0 drivers/media/dvb-core/dvbdev.c:996
 dvb_demux_ioctl+0x29/0x40 drivers/media/dvb-core/dmxdev.c:1208
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 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: 0033:0x7fad3799e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fad388b8028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fad37c26180 RCX: 00007fad3799e0d9
RDX: 00002000000000c0 RSI: 0000000040146f2c RDI: 0000000000000003
RBP: 00007fad37a35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fad37c26218 R14: 00007fad37c26180 R15: 00007fff575e5288
 </TASK>
----------------
Code disassembly (best guess):
   0:	29 79 90             	sub    %edi,-0x70(%rcx)
   3:	48 c1 e8 03          	shr    $0x3,%rax
   7:	0f b6 04 18          	movzbl (%rax,%rbx,1),%eax
   b:	84 c0                	test   %al,%al
   d:	0f 85 47 02 00 00    	jne    0x25a
  13:	83 3d 77 a5 9a 04 00 	cmpl   $0x0,0x49aa577(%rip)        # 0x49aa591
  1a:	75 13                	jne    0x2f
  1c:	48 8d 3d ba 9b 9d 04 	lea    0x49d9bba(%rip),%rdi        # 0x49d9bdd
  23:	48 c7 c6 80 fe 0c 8c 	mov    $0xffffffff8c0cfe80,%rsi
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	90                   	nop
  30:	e9 67 ee ff ff       	jmp    0xffffee9c
  35:	90                   	nop
  36:	0f 0b                	ud2
  38:	90                   	nop
  39:	e9 3a f2 ff ff       	jmp    0xfffff278
  3e:	90                   	nop
  3f:	0f                   	.byte 0xf


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