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From: Bart Van Assche <bvanassche@acm.org>
To: Jan Kara <jack@suse.cz>, Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, tristmd@gmail.com, stable@vger.kernel.org
Subject: Re: [PATCH] blktrace: Protect q->blk_trace with RCU
Date: Sun, 9 Feb 2020 19:54:18 -0800	[thread overview]
Message-ID: <6a49e67f-e621-939e-11d5-b614fa8da7d8@acm.org> (raw)
In-Reply-To: <20200206142812.25989-1-jack@suse.cz>

On 2020-02-06 06:28, Jan Kara wrote:
> KASAN is reporting that __blk_add_trace() has a use-after-free issue
> when accessing q->blk_trace. Indeed the switching of block tracing (and
> thus eventual freeing of q->blk_trace) is completely unsynchronized with
> the currently running tracing and thus it can happen that the blk_trace
> structure is being freed just while __blk_add_trace() works on it.
> Protect accesses to q->blk_trace by RCU during tracing and make sure we
> wait for the end of RCU grace period when shutting down tracing. Luckily
> that is rare enough event that we can afford that. Note that postponing
> the freeing of blk_trace to an RCU callback should better be avoided as
> it could have unexpected user visible side-effects as debugfs files
> would be still existing for a short while block tracing has been shut
> down.

Reviewed-by: Bart Van Assche <bvanassche@acm.org>

  parent reply	other threads:[~2020-02-10  3:54 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-06 14:28 [PATCH] blktrace: Protect q->blk_trace with RCU Jan Kara
2020-02-06 18:46 ` Chaitanya Kulkarni
2020-02-06 18:49   ` Jens Axboe
2020-02-06 19:37     ` Chaitanya Kulkarni
2020-02-10  0:38 ` Chaitanya Kulkarni
2020-02-10  2:19 ` Ming Lei
2020-02-10  3:54 ` Bart Van Assche [this message]
2020-02-19 12:59 ` Jan Kara
2020-02-25 10:20   ` Ming Lei
2020-02-25 15:40     ` Jens Axboe
2020-03-02 20:40 ` Bjorn Helgaas
2020-03-02 21:19   ` Chaitanya Kulkarni
2020-03-02 21:59     ` Bjorn Helgaas
2020-03-02 22:06     ` Keith Busch
2020-03-03 11:07       ` Cengiz Can
2020-03-03 12:17         ` Greg KH
2020-03-05  1:51         ` Ming Lei
2020-03-05  4:27           ` Cengiz Can

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