[syzbot] [media?] WARNING in dvb_frontend_release

[syzbot <syzbot+2528bcebd696f88fdb4c@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    0a0d1d55dad5 Merge tag 'scftorture.2026.08.18a' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17a3b19e580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a73a22d959389384
dashboard link: https://syzkaller.appspot.com/bug?extid=2528bcebd696f88fdb4c
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b6c177362f10/disk-0a0d1d55.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f2c3243ec7e8/vmlinux-0a0d1d55.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c41f358fc565/bzImage-0a0d1d55.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2528bcebd696f88fdb4c@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#0: syz.8.552/9005
WARNING: kernel/locking/mutex.c:625 at __mutex_lock+0x944/0x1bc0 kernel/locking/mutex.c:821, CPU#0: syz.8.552/9005
Modules linked in:
CPU: 0 UID: 0 PID: 9005 Comm: syz.8.552 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
RIP: 0010:__mutex_lock_common kernel/locking/mutex.c:625 [inline]
RIP: 0010:__mutex_lock+0x94b/0x1bc0 kernel/locking/mutex.c:821
Code: 0f b6 14 11 38 d0 7c 08 84 d2 0f 85 b4 10 00 00 44 8b 05 b8 a2 78 05 45 85 c0 75 13 48 8d 3d ac a7 7b 05 48 c7 c6 e0 d3 ef 8b <67> 48 0f b9 3a 90 e9 1b f8 ff ff 4d 8d a7 f0 0a 00 00 4c 89 e7 e8
RSP: 0018:ffffc90003417b40 EFLAGS: 00010246
RAX: 0000000000000003 RBX: ffff88801efcd318 RCX: 1ffffffff2289aec
RDX: 0000000000000000 RSI: ffffffff8befd3e0 RDI: ffffffff9147dc60
RBP: ffffc90003417cb0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff88801efcd1c0
FS:  0000000000000000(0000) GS:ffff888123b7b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b32d24000 CR3: 000000007627c000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 dvb_frontend_release+0x2f2/0x5d0 drivers/media/dvb-core/dvb_frontend.c:2944
 __fput+0x3ff/0xb50 fs/file_table.c:512
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x951/0x2ae0 kernel/exit.c:1008
 __do_sys_exit kernel/exit.c:1118 [inline]
 __se_sys_exit kernel/exit.c:1116 [inline]
 __x64_sys_exit+0x42/0x50 kernel/exit.c:1116
 x64_sys_call+0x156c/0x1570 arch/x86/include/generated/asm/syscalls_64.h:61
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9732d9e0d9
Code: Unable to access opcode bytes at 0x7f9732d9e0af.
RSP: 002b:00007f9730ff5ef8 EFLAGS: 00000246 ORIG_RAX: 000000000000003c
RAX: ffffffffffffffda RBX: 0000000000000058 RCX: 00007f9732d9e0d9
RDX: 00007f9730ff69c8 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f9732e35024 R08: 0000000000000000 R09: 0000000000000058
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9733026038 R14: 00007f9733025fa0 R15: 00007fff990920b8
 </TASK>
----------------
Code disassembly (best guess):
   0:	0f b6 14 11          	movzbl (%rcx,%rdx,1),%edx
   4:	38 d0                	cmp    %dl,%al
   6:	7c 08                	jl     0x10
   8:	84 d2                	test   %dl,%dl
   a:	0f 85 b4 10 00 00    	jne    0x10c4
  10:	44 8b 05 b8 a2 78 05 	mov    0x578a2b8(%rip),%r8d        # 0x578a2cf
  17:	45 85 c0             	test   %r8d,%r8d
  1a:	75 13                	jne    0x2f
  1c:	48 8d 3d ac a7 7b 05 	lea    0x57ba7ac(%rip),%rdi        # 0x57ba7cf
  23:	48 c7 c6 e0 d3 ef 8b 	mov    $0xffffffff8befd3e0,%rsi
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	90                   	nop
  30:	e9 1b f8 ff ff       	jmp    0xfffff850
  35:	4d 8d a7 f0 0a 00 00 	lea    0xaf0(%r15),%r12
  3c:	4c 89 e7             	mov    %r12,%rdi
  3f:	e8                   	.byte 0xe8


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