From: Bart Van Assche <bvanassche@acm.org>
To: "Guilherme G. Piccoli" <gpiccoli@canonical.com>,
linux-block@vger.kernel.org, linux-raid@vger.kernel.org
Cc: dm-devel@redhat.com, axboe@kernel.dk, gavin.guo@canonical.com,
jay.vosburgh@canonical.com, kernel@gpiccoli.net,
stable@vger.kernel.org
Subject: Re: [PATCH 1/2] block: Fix a NULL pointer dereference in generic_make_request()
Date: Tue, 30 Apr 2019 15:55:25 -0700 [thread overview]
Message-ID: <1556664925.161891.183.camel@acm.org> (raw)
In-Reply-To: <20190430223722.20845-1-gpiccoli@canonical.com>
On Tue, 2019-04-30 at 19:37 -0300, Guilherme G. Piccoli wrote:
> Commit 37f9579f4c31 ("blk-mq: Avoid that submitting a bio concurrently
> with device removal triggers a crash") introduced a NULL pointer
> dereference in generic_make_request(). The patch sets q to NULL and
> enter_succeeded to false; right after, there's an 'if (enter_succeeded)'
> which is not taken, and then the 'else' will dereference q in
> blk_queue_dying(q).
>
> This patch just moves the 'q = NULL' to a point in which it won't trigger
> the oops, although the semantics of this NULLification remains untouched.
>
> A simple test case/reproducer is as follows:
> a) Build kernel v5.1-rc7 with CONFIG_BLK_CGROUP=n.
>
> b) Create a raid0 md array with 2 NVMe devices as members, and mount it
> with an ext4 filesystem.
>
> c) Run the following oneliner (supposing the raid0 is mounted in /mnt):
> (dd of=/mnt/tmp if=/dev/zero bs=1M count=999 &); sleep 0.3;
> echo 1 > /sys/block/nvme0n1/device/device/remove
> (whereas nvme0n1 is the 2nd array member)
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
next prev parent reply other threads:[~2019-04-30 23:11 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-30 22:37 [PATCH 1/2] block: Fix a NULL pointer dereference in generic_make_request() Guilherme G. Piccoli
2019-04-30 22:37 ` [PATCH 2/2] md/raid0: Do not bypass blocking queue entered for raid0 bios Guilherme G. Piccoli
2019-05-06 16:50 ` Song Liu
2019-05-06 18:48 ` Guilherme G. Piccoli
2019-05-06 21:07 ` Song Liu
2019-05-07 21:51 ` Guilherme G. Piccoli
2019-05-08 9:29 ` Wols Lists
2019-05-08 14:52 ` Guilherme G. Piccoli
2019-05-08 16:52 ` Wols Lists
2019-05-17 16:19 ` Guilherme G. Piccoli
2019-05-20 16:23 ` Song Liu
2019-05-20 19:25 ` Guilherme Piccoli
2019-04-30 22:55 ` Bart Van Assche [this message]
2019-05-17 3:33 ` [PATCH 1/2] block: Fix a NULL pointer dereference in generic_make_request() Eric Ren
2019-05-17 16:17 ` Guilherme G. Piccoli
2019-05-20 2:43 ` Eric Ren
2019-05-17 22:04 ` Ming Lei
2019-05-23 17:23 Song Liu
2019-05-23 17:25 ` Song Liu
2019-06-12 16:36 ` Guilherme G. Piccoli
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