Commit 6be6d112 authored by Chengming Zhou's avatar Chengming Zhou Committed by Jens Axboe
Browse files

blk-mq: fix tags UAF when shrinking q->nr_hw_queues 



When nr_hw_queues shrink, we free the excess tags before realloc'ing
hw_ctxs for each queue. During that resize, we may need to access those
tags, like blk_mq_tag_idle(hctx) will access queue shared tags.

This can cause a slab use-after-free, as reported by KASAN. Fix it by
moving the releasing of excess tags to the end.

Fixes: e1dd7bc9 ("blk-mq: fix tags leak when shrink nr_hw_queues")
Reported-by: default avatarYi Zhang <yi.zhang@redhat.com>
Closes: https://lore.kernel.org/all/CAHj4cs_CK63uoDpGBGZ6DN4OCTpzkR3UaVgK=LX8Owr8ej2ieQ@mail.gmail.com/


Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: default avatarChengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20230908005702.2183908-1-chengming.zhou@linux.dev


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 0bb80ecc

block/blk-mq.c

+7 −6
Original line number Diff line number Diff line
@@ -4405,11 +4405,8 @@ static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set, 
	struct blk_mq_tags **new_tags;

	int i;



	if (set->nr_hw_queues >= new_nr_hw_queues) {

		for (i = new_nr_hw_queues; i < set->nr_hw_queues; i++)

			__blk_mq_free_map_and_rqs(set, i);

	if (set->nr_hw_queues >= new_nr_hw_queues)

		goto done;

	}



	new_tags = kcalloc_node(new_nr_hw_queues, sizeof(struct blk_mq_tags *),

				GFP_KERNEL, set->numa_node);
@@ -4719,7 +4716,8 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, 
{

	struct request_queue *q;

	LIST_HEAD(head);

	int prev_nr_hw_queues;

	int prev_nr_hw_queues = set->nr_hw_queues;

	int i;



	lockdep_assert_held(&set->tag_list_lock);
@@ -4746,7 +4744,6 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, 
		blk_mq_sysfs_unregister_hctxs(q);

	}



	prev_nr_hw_queues = set->nr_hw_queues;

	if (blk_mq_realloc_tag_set_tags(set, nr_hw_queues) < 0)

		goto reregister;
@@ -4781,6 +4778,10 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, 


	list_for_each_entry(q, &set->tag_list, tag_set_list)

		blk_mq_unfreeze_queue(q);



	/* Free the excess tags when nr_hw_queues shrink. */

	for (i = set->nr_hw_queues; i < prev_nr_hw_queues; i++)

		__blk_mq_free_map_and_rqs(set, i);

}



void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)