linux-kernel - Re: [PATCH 5.13] io_uring: Check current->io_uring in io_uring_cancel

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Message-ID: <8204f859-7249-580e-9cb1-7e255dbcb982@gmail.com>
Date:   Tue, 27 Apr 2021 18:00:03 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, Palash Oswal <hello@...alpalash.com>
Cc:     dvyukov@...gle.com, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org, oswalpalash@...il.com,
        syzbot+be51ca5a4d97f017cd50@...kaller.appspotmail.com,
        syzkaller-bugs@...glegroups.com, stable@...r.kernel.org
Subject: Re: [PATCH 5.13] io_uring: Check current->io_uring in
 io_uring_cancel_sqpoll

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@...kaller.appspotmail.com

-- 
Pavel Begunkov