linux-kernel - Re: [PATCH 1/1] io_uring: fix lockup with timeouts

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Message-ID: <4a96385c-52ea-cba8-455d-6fd3042bd49e@kernel.dk>
Date:   Sat, 7 Mar 2020 08:36:27 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Pavel Begunkov <asml.silence@...il.com>, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] io_uring: fix lockup with timeouts

On 3/6/20 3:15 PM, Pavel Begunkov wrote:
> There is a recipe to deadlock the kernel: submit a timeout sqe with a
> linked_timeout (e.g.  test_single_link_timeout_ception() from liburing),
> and SIGKILL the process.
> 
> Then, io_kill_timeouts() takes @ctx->completion_lock, but the timeout
> isn't flagged with REQ_F_COMP_LOCKED, and will try to double grab it
> during io_put_free() to cancel the linked timeout. Probably, the same
> can happen with another io_kill_timeout() call site, that is
> io_commit_cqring().

Thanks, looks good, applied.

-- 
Jens Axboe