[PATCH 5.15 17/75] block: fix use-after-free of q->q_usage_counter

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5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

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.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 block/blk-core.c  |    2 --
 block/blk-sysfs.c |    2 ++
 2 files changed, 2 insertions(+), 2 deletions(-)

--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -405,8 +405,6 @@ void blk_cleanup_queue(struct request_qu
 		blk_mq_sched_free_requests(q);
 	mutex_unlock(&q->sysfs_lock);
 
-	percpu_ref_exit(&q->q_usage_counter);
-
 	/* @q is and will stay empty, shutdown and put */
 	blk_put_queue(q);
 }
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -748,6 +748,8 @@ static void blk_free_queue_rcu(struct rc
 {
 	struct request_queue *q = container_of(rcu_head, struct request_queue,
 					       rcu_head);
+
+	percpu_ref_exit(&q->q_usage_counter);
 	kmem_cache_free(blk_requestq_cachep, q);
 }
 





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