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

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Message-ID: <decd444f-701d-6960-0648-b145b6fcccfb@kernel.dk>
Date:   Tue, 27 Apr 2021 07:37:54 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Palash Oswal <hello@...alpalash.com>, asml.silence@...il.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 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.

-- 
Jens Axboe