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

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Message-ID: <de97e0f0-1c47-1a96-eb24-e62c37d2a06b@kernel.dk>
Date:   Tue, 27 Apr 2021 11:00:59 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Pavel Begunkov <asml.silence@...il.com>,
        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 11:00 AM, Pavel Begunkov wrote:
> 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

That tag was already there.

-- 
Jens Axboe