[PATCH 6.1] block: fix use-after-free of q->q_usage_counter

[Saranya Muruganandam]

From: Ming Lei <ming.lei@xxxxxxxxxx>

commit d36a9ea5e7766961e753ee38d4c331bbe6ef659b upstream.

For blk-mq, queue release handler is usually called after
blk_mq_freeze_queue_wait() returns. However, the
q_usage_counter->release() handler may not be run yet at that time, so
this can cause a use-after-free.

Fix the issue by moving percpu_ref_exit() into blk_free_queue_rcu().
Since ->release() is called with rcu read lock held, it is agreed that
the race should be covered in caller per discussion from the two links.

Backport-notes: Not a clean cherry-pick since a lot has changed,
however essentially the same fix.

Reported-by: Zhang Wensheng <zhangwensheng@xxxxxxxxxxxxxxx>
Reported-by: Zhong Jinghua <zhongjinghua@xxxxxxxxxx>
Link: https://lore.kernel.org/linux-block/Y5prfOjyyjQKUrtH@T590/T/#u
Link: https://lore.kernel.org/lkml/Y4%2FmzMd4evRg9yDi@fedora/
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: Yu Kuai <yukuai3@xxxxxxxxxx>
Cc: Dennis Zhou <dennis@xxxxxxxxxx>
Fixes: 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of percpu_ref in fast path")
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20221215021629.74870-1-ming.lei@xxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Saranya Muruganandam <saranyamohan@xxxxxxxxxx>
---
 block/blk-sysfs.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index a582ea0da74f..a82bdec923b2 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -737,6 +737,7 @@ static void blk_free_queue_rcu(struct rcu_head *rcu_head)
 	struct request_queue *q = container_of(rcu_head, struct request_queue,
 					       rcu_head);
 
+	percpu_ref_exit(&q->q_usage_counter);
 	kmem_cache_free(blk_get_queue_kmem_cache(blk_queue_has_srcu(q)), q);
 }
 
@@ -762,8 +763,6 @@ static void blk_release_queue(struct kobject *kobj)
 
 	might_sleep();
 
-	percpu_ref_exit(&q->q_usage_counter);
-
 	if (q->poll_stat)
 		blk_stat_remove_callback(q, q->poll_cb);
 	blk_stat_free_callback(q->poll_cb);
-- 
2.42.0.515.g380fc7ccd1-goog