Commit 5a0ac57c authored by Yu Kuai's avatar Yu Kuai Committed by Jens Axboe
Browse files

blk-ioc: protect ioc_destroy_icq() by 'queue_lock' 



Currently, icq is tracked by both request_queue(icq->q_node) and
task(icq->ioc_node), and ioc_clear_queue() from elevator exit is not
safe because it can access the list without protection:

ioc_clear_queue			ioc_release_fn
 lock queue_lock
 list_splice
 /* move queue list to a local list */
 unlock queue_lock
 /*
  * lock is released, the local list
  * can be accessed through task exit.
  */

				lock ioc->lock
				while (!hlist_empty)
				 icq = hlist_entry
				 lock queue_lock
				  ioc_destroy_icq
				   delete icq->ioc_node
 while (!list_empty)
  icq = list_entry()		   list_del icq->q_node
  /*
   * This is not protected by any lock,
   * list_entry concurrent with list_del
   * is not safe.
   */

				 unlock queue_lock
				unlock ioc->lock

Fix this problem by protecting list 'icq->q_node' by queue_lock from
ioc_clear_queue().

Reported-and-tested-by: default avatarPradeep Pragallapati <quic_pragalla@quicinc.com>
Link: https://lore.kernel.org/lkml/20230517084434.18932-1-quic_pragalla@quicinc.com/


Signed-off-by: default avatarYu Kuai <yukuai3@huawei.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230531073435.2923422-1-yukuai1@huaweicloud.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 6c500000

block/blk-ioc.c

+13 −17
Original line number Diff line number Diff line
@@ -77,6 +77,10 @@ static void ioc_destroy_icq(struct io_cq *icq) 
	struct elevator_type *et = q->elevator->type;



	lockdep_assert_held(&ioc->lock);

	lockdep_assert_held(&q->queue_lock);



	if (icq->flags & ICQ_DESTROYED)

		return;



	radix_tree_delete(&ioc->icq_tree, icq->q->id);

	hlist_del_init(&icq->ioc_node);
@@ -128,11 +132,6 @@ static void ioc_release_fn(struct work_struct *work) 
			spin_lock(&q->queue_lock);

			spin_lock(&ioc->lock);



			/*

			 * The icq may have been destroyed when the ioc lock

			 * was released.

			 */

			if (!(icq->flags & ICQ_DESTROYED))

			ioc_destroy_icq(icq);



			spin_unlock(&q->queue_lock);
@@ -171,23 +170,20 @@ static bool ioc_delay_free(struct io_context *ioc) 
 */

void ioc_clear_queue(struct request_queue *q)

{

	LIST_HEAD(icq_list);



	spin_lock_irq(&q->queue_lock);

	list_splice_init(&q->icq_list, &icq_list);

	spin_unlock_irq(&q->queue_lock);



	rcu_read_lock();

	while (!list_empty(&icq_list)) {

	while (!list_empty(&q->icq_list)) {

		struct io_cq *icq =

			list_entry(icq_list.next, struct io_cq, q_node);

			list_first_entry(&q->icq_list, struct io_cq, q_node);



		/*

		 * Other context won't hold ioc lock to wait for queue_lock, see

		 * details in ioc_release_fn().

		 */

		spin_lock_irq(&icq->ioc->lock);

		if (!(icq->flags & ICQ_DESTROYED))

		ioc_destroy_icq(icq);

		spin_unlock_irq(&icq->ioc->lock);

	}

	rcu_read_unlock();

	spin_unlock_irq(&q->queue_lock);

}

#else /* CONFIG_BLK_ICQ */

static inline void ioc_exit_icqs(struct io_context *ioc)