From: Bart Van Assche <bvanassche@acm.org>
To: John Garry <john.garry@huawei.com>,
hare@suse.de, ming.lei@redhat.com, axboe@kernel.dk, hch@lst.de
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
pragalla@codeaurora.org, kashyap.desai@broadcom.com,
yuyufen@huawei.com
Subject: Re: [RFC PATCH v3 1/3] blk-mq: Clean up references to old requests when freeing rqs
Date: Sat, 6 Mar 2021 10:13:11 -0800 [thread overview]
Message-ID: <ab2c3bc2-6dac-3c5c-3589-9383c459f478@acm.org> (raw)
In-Reply-To: <1614957294-188540-2-git-send-email-john.garry@huawei.com>
On 3/5/21 7:14 AM, John Garry wrote:
> @@ -2296,10 +2296,14 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
>
> for (i = 0; i < tags->nr_tags; i++) {
> struct request *rq = tags->static_rqs[i];
> + int j;
>
> if (!rq)
> continue;
> set->ops->exit_request(set, rq, hctx_idx);
> + /* clean up any references which occur in @ref_tags */
> + for (j = 0; ref_tags && j < ref_tags->nr_tags; j++)
> + cmpxchg(&ref_tags->rqs[j], rq, 0);
> tags->static_rqs[i] = NULL;
> }
> }
What prevents blk_mq_tagset_busy_iter() from reading hctx->tags[...]
before the cmpxcg() call and dereferencing it after blk_mq_free_rqs()
has called __free_pages()?
Thanks,
Bart.
next prev parent reply other threads:[~2021-03-06 18:14 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-05 15:14 [RFC PATCH v3 0/3] blk-mq: Avoid use-after-free for accessing old requests John Garry
2021-03-05 15:14 ` [RFC PATCH v3 1/3] blk-mq: Clean up references to old requests when freeing rqs John Garry
2021-03-06 2:52 ` Khazhy Kumykov
2021-03-08 11:18 ` John Garry
2021-03-06 18:13 ` Bart Van Assche [this message]
2021-03-08 10:37 ` John Garry
2021-03-05 15:14 ` [RFC PATCH v3 2/3] blk-mq: Freeze and quiesce all queues for tagset in elevator_exit() John Garry
2021-03-06 4:32 ` Bart Van Assche
2021-03-08 10:50 ` John Garry
2021-03-08 19:35 ` Bart Van Assche
2021-03-10 15:57 ` Bart Van Assche
2021-03-11 0:58 ` Ming Lei
2021-03-11 8:21 ` John Garry
2021-03-12 23:05 ` Bart Van Assche
2021-03-16 16:15 ` John Garry
2021-03-16 17:00 ` Bart Van Assche
2021-03-16 17:43 ` John Garry
2021-03-16 19:59 ` Bart Van Assche
2021-03-19 18:19 ` John Garry
2021-03-19 18:32 ` Bart Van Assche
2021-03-05 15:14 ` [RFC PATCH v3 3/3] blk-mq: Lockout tagset iterator when exiting elevator John Garry
2021-03-06 4:43 ` Bart Van Assche
2021-03-08 11:17 ` John Garry
2021-03-08 19:59 ` Bart Van Assche
2021-03-09 17:47 ` John Garry
2021-03-09 19:21 ` Bart Van Assche
2021-03-10 8:52 ` John Garry
2021-03-10 16:00 ` Bart Van Assche
2021-03-10 17:26 ` John Garry
2021-03-18 10:26 ` [RFC PATCH v3 0/3] blk-mq: Avoid use-after-free for accessing old requests Shinichiro Kawasaki
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