Re: KASAN: null-ptr-deref Write in io_wq_cancel_all

From: Jens Axboe
Date: Fri Oct 25 2019 - 09:50:49 EST

On 10/25/19 5:58 AM, Dmitry Vyukov wrote:
> On Fri, Oct 25, 2019 at 1:51 PM syzbot
> <syzbot+d958a65633ea70280b23@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>> Hello,
>> syzbot found the following crash on:
>> HEAD commit: 139c2d13 Add linux-next specific files for 20191025
>> git tree: linux-next
>> console output:
>> kernel config:
>> dashboard link:
>> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
>> Unfortunately, I don't have any reproducer for this crash yet.
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+d958a65633ea70280b23@xxxxxxxxxxxxxxxxxxxxxxxxx
> +Jens

Let me know if/when you have a reproducer for this one. I initially thought
this was a basic NULL pointer check, but it doesn't look like it. I wonder
if the thread handling the request got a signal, and since it had the
task file_table with the io_uring fd attached, it's triggering an exit.

I'll poke at it, but don't immediately see the issue.

Jens Axboe