linux-kernel - [PATCH] blk-mq: use after free when freeing tag sets

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Date:	Fri,  2 Oct 2015 21:40:35 -0400
From:	Sasha Levin <sasha.levin@...cle.com>
To:	axboe@...nel.dk
Cc:	keith.busch@...el.com, linux-kernel@...r.kernel.org,
	Sasha Levin <sasha.levin@...cle.com>
Subject: [PATCH] blk-mq: use after free when freeing tag sets

Commit f26cdc853 ("blk-mq: Shared tag enhancements") has introduced a use after
free where it tried to free the cpumask var out of the tag set but the tag set
was already freed by blk_mq_free_rq_map().

Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
---
 block/blk-mq-tag.c |    1 +
 block/blk-mq.c     |    7 ++-----
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index f6020c6..c03eeb8 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -628,6 +628,7 @@ void blk_mq_free_tags(struct blk_mq_tags *tags)
 {
 	bt_free(&tags->bitmap_tags);
 	bt_free(&tags->breserved_tags);
+	free_cpumask_var(tags->cpumask);
 	kfree(tags);
 }
 
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5692c15..197a615 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2270,12 +2270,9 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
 {
 	int i;
 
-	for (i = 0; i < set->nr_hw_queues; i++) {
-		if (set->tags[i]) {
+	for (i = 0; i < set->nr_hw_queues; i++)
+		if (set->tags[i])
 			blk_mq_free_rq_map(set, set->tags[i], i);
-			free_cpumask_var(set->tags[i]->cpumask);
-		}
-	}
 
 	kfree(set->tags);
 	set->tags = NULL;
-- 
1.7.10.4

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