[moderation] [media?] general protection fault in dvb_dmxdev_filter_stop

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7d6661873f6b Add linux-next specific files for 20260226
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=100aa8d6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=16deeeab1ae84468
dashboard link: https://syzkaller.appspot.com/bug?extid=74014f72890a415f7401
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [linux-...@vger.kernel.org linux...@vger.kernel.org mch...@kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b6ad57c4e070/disk-7d666187.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6faf92508823/vmlinux-7d666187.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7a9ea041a5d1/bzImage-7d666187.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+74014f...@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
CPU: 1 UID: 0 PID: 6999 Comm: syz.0.396 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:dvb_dmxdev_feed_stop drivers/media/dvb-core/dmxdev.c:494 [inline]
RIP: 0010:dvb_dmxdev_filter_stop+0x1a9/0x720 drivers/media/dvb-core/dmxdev.c:572
Code: 00 00 49 8d 5c 24 f8 48 89 d8 48 c1 e8 03 80 3c 28 00 74 08 48 89 df e8 75 f7 47 fa 48 8b 1b 48 8d 7b 28 48 89 f8 48 c1 e8 03 <80> 3c 28 00 74 05 e8 5c f7 47 fa 4c 8b 5b 28 48 89 df 2e e8 db ac
RSP: 0018:ffffc90004327c58 EFLAGS: 00010206
RAX: 0000000000000005 RBX: 0000000000000000 RCX: 0000000000000005
RDX: ffffffff87e8110a RSI: ffffffff8f8e1200 RDI: 0000000000000028
RBP: dffffc0000000000 R08: ffff88803287bd00 R09: 0000000000000002
R10: 0000000000000002 R11: 0000000000000000 R12: ffff888025c1f510
R13: ffffc900064dc540 R14: 1ffff92000c9b8a8 R15: ffffc900064dc4e8
FS: 0000555581367500(0000) GS:ffff88812511b000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c2df5db CR3: 000000007ef5e000 CR4: 00000000003526f0
Call Trace:
<TASK>
dvb_dmxdev_filter_free drivers/media/dvb-core/dmxdev.c:856 [inline]
dvb_demux_release+0x93/0x640 drivers/media/dvb-core/dmxdev.c:1249
__fput+0x44f/0xa70 fs/file_table.c:469
task_work_run+0x1d9/0x270 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fcd3419c799
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:00007fff2d388378 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fcd34417da0 RCX: 00007fcd3419c799
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fcd34417da0 R08: 00007fcd34416038 R09: 0000000000000000
R10: 00000000003ffd18 R11: 0000000000000246 R12: 0000000000029303
R13: 00007fcd34415fac R14: 0000000000029010 R15: 00007fff2d388480
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:dvb_dmxdev_feed_stop drivers/media/dvb-core/dmxdev.c:494 [inline]
RIP: 0010:dvb_dmxdev_filter_stop+0x1a9/0x720 drivers/media/dvb-core/dmxdev.c:572
Code: 00 00 49 8d 5c 24 f8 48 89 d8 48 c1 e8 03 80 3c 28 00 74 08 48 89 df e8 75 f7 47 fa 48 8b 1b 48 8d 7b 28 48 89 f8 48 c1 e8 03 <80> 3c 28 00 74 05 e8 5c f7 47 fa 4c 8b 5b 28 48 89 df 2e e8 db ac
RSP: 0018:ffffc90004327c58 EFLAGS: 00010206
RAX: 0000000000000005 RBX: 0000000000000000 RCX: 0000000000000005
RDX: ffffffff87e8110a RSI: ffffffff8f8e1200 RDI: 0000000000000028
RBP: dffffc0000000000 R08: ffff88803287bd00 R09: 0000000000000002
R10: 0000000000000002 R11: 0000000000000000 R12: ffff888025c1f510
R13: ffffc900064dc540 R14: 1ffff92000c9b8a8 R15: ffffc900064dc4e8
FS: 0000555581367500(0000) GS:ffff88812511b000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30263fff CR3: 000000007ef5e000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
0: 00 00 add %al,(%rax)
2: 49 8d 5c 24 f8 lea -0x8(%r12),%rbx
7: 48 89 d8 mov %rbx,%rax
a: 48 c1 e8 03 shr $0x3,%rax
e: 80 3c 28 00 cmpb $0x0,(%rax,%rbp,1)
12: 74 08 je 0x1c
14: 48 89 df mov %rbx,%rdi
17: e8 75 f7 47 fa call 0xfa47f791
1c: 48 8b 1b mov (%rbx),%rbx
1f: 48 8d 7b 28 lea 0x28(%rbx),%rdi
23: 48 89 f8 mov %rdi,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 80 3c 28 00 cmpb $0x0,(%rax,%rbp,1) <-- trapping instruction
2e: 74 05 je 0x35
30: e8 5c f7 47 fa call 0xfa47f791
35: 4c 8b 5b 28 mov 0x28(%rbx),%r11
39: 48 89 df mov %rbx,%rdi
3c: 2e cs
3d: e8 .byte 0xe8
3e: db .byte 0xdb
3f: ac lods %ds:(%rsi),%al


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