Re: [PATCH 5.13] io_uring: Check current->io_uring in io_uring_cancel_sqpoll

From: Pavel Begunkov
Date: Tue Apr 27 2021 - 13:00:44 EST

On 4/27/21 2:37 PM, Jens Axboe wrote:
> On 4/27/21 6:51 AM, Palash Oswal wrote:
>> syzkaller identified KASAN: null-ptr-deref Write in
>> io_uring_cancel_sqpoll on v5.12
>> io_uring_cancel_sqpoll is called by io_sq_thread before calling
>> io_uring_alloc_task_context. This leads to current->io_uring being
>> NULL. io_uring_cancel_sqpoll should not have to deal with threads
>> where current->io_uring is NULL.
>> In order to cast a wider safety net, perform input sanitisation
>> directly in io_uring_cancel_sqpoll and return for NULL value of
>> current->io_uring.
> Thanks applied - I augmented the commit message a bit.

btw, does it fixes the replied before syz report? Should
syz fix or tag it if so.
Reported-by: syzbot+be51ca5a4d97f017cd50@xxxxxxxxxxxxxxxxxxxxxxxxx

Pavel Begunkov