Message-ID: <e6f8da96-6920-434d-9f15-6e283bf3c829@kernel.dk>
Date: Mon, 9 Feb 2026 11:50:02 -0700
From: Jens Axboe <axboe@...nel.dk>
To: syzbot <syzbot+ab12f0c08dd7ab8d057c@...kaller.appspotmail.com>,
 io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzkaller-bugs@...glegroups.com, Mauro Carvalho Chehab <mchehab@...nel.org>,
 linux-media@...r.kernel.org
Subject: Re: [syzbot] [io-uring?] BUG: corrupted list in
 io_poll_remove_entries

On 2/9/26 11:26 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    e7aa57247700 Merge tag 'spi-fix-v6.19-rc8' of git://git.ke..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14d3b65a580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f1fac0919970b671
> dashboard link: https://syzkaller.appspot.com/bug?extid=ab12f0c08dd7ab8d057c
> compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1222965a580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=140e833a580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/c46beb4ff3a5/disk-e7aa5724.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/d162bcaaf9b9/vmlinux-e7aa5724.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/54b0844b8ea7/bzImage-e7aa5724.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+ab12f0c08dd7ab8d057c@...kaller.appspotmail.com
> 
> list_del corruption. prev->next should be ffff88807dc6c3f0, but was ffff888146b205c8. (prev=ffff888146b205c8)
> ------------[ cut here ]------------
> kernel BUG at lib/list_debug.c:62!
> Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
> CPU: 0 UID: 0 PID: 5969 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
> RIP: 0010:__list_del_entry_valid_or_report+0x14a/0x1d0 lib/list_debug.c:62
> Code: 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 8d 00 00 00 48 8b 55 00 48 89 e9 48 89 de 48 c7 c7 40 3d fa 8b e8 37 b0 32 fc 90 <0f> 0b 4c 89 e7 e8 3c 24 5d fd 48 89 ea 48 b8 00 00 00 00 00 fc ff
> RSP: 0018:ffffc90003bffaa8 EFLAGS: 00010082
> RAX: 000000000000006d RBX: ffff88807dc6c3f0 RCX: 0000000000000000
> RDX: 000000000000006d RSI: ffffffff81e5d6c9 RDI: fffff5200077ff46
> RBP: ffff888146b205c8 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000080000001 R11: 0000000000000000 R12: ffff88807dc6c2b0
> R13: ffff88807dc6c408 R14: ffff88807dc6c3f0 R15: ffff88807dc6c3c8
> FS:  0000000000000000(0000) GS:ffff8881245d9000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f60e56708c0 CR3: 000000006b065000 CR4: 00000000003526f0
> Call Trace:
>  <TASK>
>  __list_del_entry_valid include/linux/list.h:132 [inline]
>  __list_del_entry include/linux/list.h:223 [inline]
>  list_del_init include/linux/list.h:295 [inline]
>  io_poll_remove_waitq io_uring/poll.c:149 [inline]
>  io_poll_remove_entry io_uring/poll.c:166 [inline]
>  io_poll_remove_entries.part.0+0x156/0x7e0 io_uring/poll.c:197
>  io_poll_remove_entries io_uring/poll.c:177 [inline]
>  io_poll_task_func+0x39e/0xe30 io_uring/poll.c:343
>  io_handle_tw_list+0x194/0x580 io_uring/io_uring.c:1122
>  tctx_task_work_run+0x57/0x2b0 io_uring/io_uring.c:1182
>  tctx_task_work+0x7a/0xd0 io_uring/io_uring.c:1200
>  task_work_run+0x150/0x240 kernel/task_work.c:233
>  exit_task_work include/linux/task_work.h:40 [inline]
>  do_exit+0x829/0x2a30 kernel/exit.c:971
>  do_group_exit+0xd5/0x2a0 kernel/exit.c:1112
>  __do_sys_exit_group kernel/exit.c:1123 [inline]
>  __se_sys_exit_group kernel/exit.c:1121 [inline]
>  __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1121
>  x64_sys_call+0x14fd/0x1510 arch/x86/include/generated/asm/syscalls_64.h:232
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f60e579aeb9
> Code: Unable to access opcode bytes at 0x7f60e579ae8f.
> RSP: 002b:00007ffc2d47ddf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f60e579aeb9
> RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: 0000000000000003 R08: 0000000000000000 R09: 00007f60e59e1280
> R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007f60e59e1280 R14: 0000000000000003 R15: 00007ffc2d47deb0
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:__list_del_entry_valid_or_report+0x14a/0x1d0 lib/list_debug.c:62
> Code: 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 8d 00 00 00 48 8b 55 00 48 89 e9 48 89 de 48 c7 c7 40 3d fa 8b e8 37 b0 32 fc 90 <0f> 0b 4c 89 e7 e8 3c 24 5d fd 48 89 ea 48 b8 00 00 00 00 00 fc ff
> RSP: 0018:ffffc90003bffaa8 EFLAGS: 00010082
> RAX: 000000000000006d RBX: ffff88807dc6c3f0 RCX: 0000000000000000
> RDX: 000000000000006d RSI: ffffffff81e5d6c9 RDI: fffff5200077ff46
> RBP: ffff888146b205c8 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000080000001 R11: 0000000000000000 R12: ffff88807dc6c2b0
> R13: ffff88807dc6c408 R14: ffff88807dc6c3f0 R15: ffff88807dc6c3c8
> FS:  0000000000000000(0000) GS:ffff8881245d9000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f60e56708c0 CR3: 000000006b065000 CR4: 00000000003526f0

This looks like a bug related to dvb polling, presumably in dvb_dvr_poll()
or friends. I've seen that in drivers before, for example comedi, see:

commit 35b6fc51c666fc96355be5cd633ed0fe4ccf68b2
Author: Ian Abbott <abbotti@....co.uk>
Date:   Tue Jul 22 16:53:16 2025 +0100

    comedi: fix race between polling and detaching

as a reference.

#syz set subsystems: media

-- 
Jens Axboe

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