Re: [syzbot] [io-uring?] BUG: corrupted list in io_poll_remove_entries

[Jens Axboe <axboe@kernel.dk>]

On 2/9/26 1:18 PM, Jens Axboe wrote:
> 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@syzkaller.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
> 
> #syz test
> 
> diff --git a/drivers/media/dvb-core/dmxdev.c b/drivers/media/dvb-core/dmxdev.c
> index 8c6f5aafda1d..5cb46109d1ff 100644
> --- a/drivers/media/dvb-core/dmxdev.c
> +++ b/drivers/media/dvb-core/dmxdev.c
> @@ -168,7 +168,9 @@ static int dvb_dvr_open(struct inode *inode, struct file *file)
>  			mutex_unlock(&dmxdev->mutex);
>  			return -ENOMEM;
>  		}
> -		dvb_ringbuffer_init(&dmxdev->dvr_buffer, mem, DVR_BUFFER_SIZE);
> +		dmxdev->dvr_buffer.data = mem;
> +		dmxdev->dvr_buffer.size = DVR_BUFFER_SIZE;
> +		dvb_ringbuffer_reset(&dmxdev->dvr_buffer);
>  		if (dmxdev->may_do_mmap)
>  			dvb_vb2_init(&dmxdev->dvr_vb2_ctx, "dvr",
>  				     file->f_flags & O_NONBLOCK);
> 

Mauro and other maintainers, this is literally the same issue as one reported
last year:

https://lore.kernel.org/linux-media/20250407091619.11250-1-superman.xpt@gmail.com/

and I'm honestly a bit surprised that nobody has dealt with this, it's 10 months ago.
And syzbot is still hitting it, literally crashing the box.

Hmm?

-- 
Jens Axboe