From: Junichi Nomura <j-nomura@ce.jp.nec.com>
Date: Wed, 14 Oct 2015 05:02:15 +0000 (+0000)
Subject: blk-mq: fix use-after-free in blk_mq_free_tag_set()
X-Git-Tag: v4.2.6~11
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=39caa731fbb5bfb5cf376a18dcc63a3a0a69ee27;p=thirdparty%2Fkernel%2Fstable.git

blk-mq: fix use-after-free in blk_mq_free_tag_set()

commit f42d79ab67322e51b92dd7aa965e310c71352a64 upstream.

tags is freed in blk_mq_free_rq_map() and should not be used after that.
The problem doesn't manifest if CONFIG_CPUMASK_OFFSTACK is false because
free_cpumask_var() is nop.

tags->cpumask is allocated in blk_mq_init_tags() so it's natural to
free cpumask in its counter part, blk_mq_free_tags().

Fixes: f26cdc8536ad ("blk-mq: Shared tag enhancements")
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Keith Busch <keith.busch@intel.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 9115c6d59948a..2735198949512 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 c699026951367..4d6ff5259a617 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2263,10 +2263,8 @@ 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]) {
+		if (set->tags[i])
 			blk_mq_free_rq_map(set, set->tags[i], i);
-			free_cpumask_var(set->tags[i]->cpumask);
-		}
 	}
 
 	kfree(set->tags);