From: David Jeffery <djeffery@redhat.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, Bart Van Assche <bvanassche@acm.org>,
Khazhy Kumykov <khazhy@google.com>,
Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>,
Hannes Reinecke <hare@suse.de>,
John Garry <john.garry@huawei.com>
Subject: Re: [PATCH V4 3/4] blk-mq: clear stale request in tags->rq[] before freeing one request pool
Date: Thu, 29 Apr 2021 10:02:55 -0400 [thread overview]
Message-ID: <20210429140057.GA43343@redhat> (raw)
In-Reply-To: <20210429023458.3044317-4-ming.lei@redhat.com>
On Thu, Apr 29, 2021 at 10:34:57AM +0800, Ming Lei wrote:
>
> refcount_inc_not_zero() in bt_tags_iter() still may read one freed
> request.
>
> Fix the issue by the following approach:
>
> 1) hold a per-tags spinlock when reading ->rqs[tag] and calling
> refcount_inc_not_zero in bt_tags_iter()
>
> 2) clearing stale request referred via ->rqs[tag] before freeing
> request pool, the per-tags spinlock is held for clearing stale
> ->rq[tag]
>
> So after we cleared stale requests, bt_tags_iter() won't observe
> freed request any more, also the clearing will wait for pending
> request reference.
>
> The idea of clearing ->rqs[] is borrowed from John Garry's previous
> patch and one recent David's patch.
With the flush request handled in a separate patch, this looks good to me.
Reviewed-by: David Jeffery <djeffery@redhat.com>
next prev parent reply other threads:[~2021-04-29 14:03 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-29 2:34 [PATCH V4 0/4] blk-mq: fix request UAF related with iterating over tagset requests Ming Lei
2021-04-29 2:34 ` [PATCH V4 1/4] block: avoid double io accounting for flush request Ming Lei
2021-04-30 2:51 ` Bart Van Assche
2021-04-30 3:12 ` Ming Lei
2021-04-29 2:34 ` [PATCH V4 2/4] blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter Ming Lei
2021-04-30 3:06 ` Bart Van Assche
2021-04-29 2:34 ` [PATCH V4 3/4] blk-mq: clear stale request in tags->rq[] before freeing one request pool Ming Lei
2021-04-29 14:02 ` David Jeffery [this message]
2021-04-29 2:34 ` [PATCH V4 4/4] blk-mq: clearing flush request reference in tags->rqs[] Ming Lei
2021-04-29 14:13 ` David Jeffery
2021-04-30 3:05 ` Bart Van Assche
2021-05-04 7:29 ` [PATCH V4 0/4] blk-mq: fix request UAF related with iterating over tagset requests Ming Lei
2021-05-04 10:15 ` John Garry
2021-05-04 11:43 ` Ming Lei
2021-05-05 11:19 ` John Garry
2021-05-05 14:28 ` Ming Lei
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