[v6.1] general protection fault in dvb_dmxdev_feed_restart

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4931e0e1673d Linux 6.1.170
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=147e4a73980000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0605c5af04d7603
dashboard link: https://syzkaller.appspot.com/bug?extid=c7b2b10d92b6de2e4a09
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4c1b2399e351/disk-4931e0e1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/feb034d7563a/vmlinux-4931e0e1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/424a14bbc862/bzImage-4931e0e1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c7b2b1...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000221: 0000 [#1] PREEMPT SMP KASAN
KASAN: probably user-memory-access in range [0x0000000000001108-0x000000000000110f]
CPU: 1 PID: 6278 Comm: syz.5.575 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:dvb_dmxdev_feed_start drivers/media/dvb-core/dmxdev.c:510 [inline]
RIP: 0010:dvb_dmxdev_feed_restart+0x402/0x6b0 drivers/media/dvb-core/dmxdev.c:539
Code: e8 03 48 bb 00 00 00 00 00 fc ff df 80 3c 18 00 74 05 e8 11 5e 0d fb 49 8b 4c 2f 08 48 8d b9 08 11 00 00 48 89 f8 48 c1 e8 03 <80> 3c 18 00 74 0b 48 89 cb e8 f0 5d 0d fb 48 89 d9 48 89 cf 48 83
RSP: 0018:ffffc9001e897c08 EFLAGS: 00010206
RAX: 0000000000000221 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8d8af3e0 RDI: 0000000000001108
RBP: 0000000000000000 R08: ffff88807ccb0000 R09: 0000000000000002
R10: 0000000000000002 R11: 0000000000000000 R12: 0000000000000001
R13: ffffc9000630c060 R14: 1ffff92000c6180b R15: ffffc9000630c000
FS: 000055557c738500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fea8bc17dac CR3: 0000000074b3f000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
dvb_dmxdev_filter_stop+0x620/0x710 drivers/media/dvb-core/dmxdev.c:566
dvb_dmxdev_filter_free drivers/media/dvb-core/dmxdev.c:842 [inline]
dvb_demux_release+0x92/0x640 drivers/media/dvb-core/dmxdev.c:1248
__fput+0x22c/0x920 fs/file_table.c:320
task_work_run+0x1d0/0x260 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f468579cdd9
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:00007ffee702ee28 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffee702ef10 RCX: 00007f468579cdd9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 000000000002821b R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b32420000 R11: 0000000000000246 R12: 00007ffee702ef50
R13: 00007f4685a15fac R14: 000000000002829c R15: 00007f4685a15fa0
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:dvb_dmxdev_feed_start drivers/media/dvb-core/dmxdev.c:510 [inline]
RIP: 0010:dvb_dmxdev_feed_restart+0x402/0x6b0 drivers/media/dvb-core/dmxdev.c:539
Code: e8 03 48 bb 00 00 00 00 00 fc ff df 80 3c 18 00 74 05 e8 11 5e 0d fb 49 8b 4c 2f 08 48 8d b9 08 11 00 00 48 89 f8 48 c1 e8 03 <80> 3c 18 00 74 0b 48 89 cb e8 f0 5d 0d fb 48 89 d9 48 89 cf 48 83
RSP: 0018:ffffc9001e897c08 EFLAGS: 00010206
RAX: 0000000000000221 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8d8af3e0 RDI: 0000000000001108
RBP: 0000000000000000 R08: ffff88807ccb0000 R09: 0000000000000002
R10: 0000000000000002 R11: 0000000000000000 R12: 0000000000000001
R13: ffffc9000630c060 R14: 1ffff92000c6180b R15: ffffc9000630c000
FS: 000055557c738500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fda6ea17dac CR3: 0000000074b3f000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: e8 03 48 bb 00 call 0xbb4808
5: 00 00 add %al,(%rax)
7: 00 00 add %al,(%rax)
9: fc cld
a: ff lcall (bad)
b: df 80 3c 18 00 74 filds 0x7400183c(%rax)
11: 05 e8 11 5e 0d add $0xd5e11e8,%eax
16: fb sti
17: 49 8b 4c 2f 08 mov 0x8(%r15,%rbp,1),%rcx
1c: 48 8d b9 08 11 00 00 lea 0x1108(%rcx),%rdi
23: 48 89 f8 mov %rdi,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 80 3c 18 00 cmpb $0x0,(%rax,%rbx,1) <-- trapping instruction
2e: 74 0b je 0x3b
30: 48 89 cb mov %rcx,%rbx
33: e8 f0 5d 0d fb call 0xfb0d5e28
38: 48 89 d9 mov %rbx,%rcx
3b: 48 89 cf mov %rcx,%rdi
3e: 48 rex.W
3f: 83 .byte 0x83


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