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Commit f054b56c authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
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blk-mq: fix race between timeout and CPU hotplug 



Firstly during CPU hotplug, even queue is freezed, timeout
handler still may come and access hctx->tags, which may cause
use after free, so this patch deactivates timeout handler
inside CPU hotplug notifier.

Secondly, tags can be shared by more than one queues, so we
have to check if the hctx has been unmapped, otherwise
still use-after-free on tags can be triggered.

Cc: <stable@vger.kernel.org>
Reported-by: default avatarDongsu Park <dongsu.park@profitbricks.com>
Tested-by: default avatarDongsu Park <dongsu.park@profitbricks.com>
Signed-off-by: default avatarMing Lei <ming.lei@canonical.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 9283b42e

block/blk-mq.c

+13 −3
Original line number Diff line number Diff line
@@ -677,10 +677,13 @@ static void blk_mq_rq_timer(unsigned long priv) 
		data.next = blk_rq_timeout(round_jiffies_up(data.next));

		mod_timer(&q->timeout, data.next);

	} else {

		queue_for_each_hw_ctx(q, hctx, i)

		queue_for_each_hw_ctx(q, hctx, i) {

			/* the hctx may be unmapped, so check it here */

			if (blk_mq_hw_queue_mapped(hctx))

				blk_mq_tag_idle(hctx);

		}

	}

}



/*

 * Reverse check our software queue for entries that we could potentially
@@ -2090,9 +2093,16 @@ static int blk_mq_queue_reinit_notify(struct notifier_block *nb, 
	 */

	list_for_each_entry(q, &all_q_list, all_q_node)

		blk_mq_freeze_queue_start(q);

	list_for_each_entry(q, &all_q_list, all_q_node)

	list_for_each_entry(q, &all_q_list, all_q_node) {

		blk_mq_freeze_queue_wait(q);



		/*

		 * timeout handler can't touch hw queue during the

		 * reinitialization

		 */

		del_timer_sync(&q->timeout);

	}



	list_for_each_entry(q, &all_q_list, all_q_node)

		blk_mq_queue_reinit(q);