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Date:   Fri, 22 Sep 2023 11:15:28 -0700
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Message-ID: <20230922181528.366670-1-saranyamohan@google.com>
Subject: [PATCH 6.1] block: fix use-after-free of q->q_usage_counter
From:   Saranya Muruganandam <saranyamohan@google.com>
To:     Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
        Ming Lei <ming.lei@redhat.com>, stable@vger.kernel.org
Cc:     linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        Zhang Wensheng <zhangwensheng@huaweicloud.com>,
        Zhong Jinghua <zhongjinghua@huawei.com>,
        Hillf Danton <hdanton@sina.com>, Yu Kuai <yukuai3@huawei.com>,
        Dennis Zhou <dennis@kernel.org>,
        Saranya Muruganandam <saranyamohan@google.com>
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Precedence: bulk

From: Ming Lei <ming.lei@redhat.com>

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@huaweicloud.com>
Reported-by: Zhong Jinghua <zhongjinghua@huawei.com>
Link: https://lore.kernel.org/linux-block/Y5prfOjyyjQKUrtH@T590/T/#u
Link: https://lore.kernel.org/lkml/Y4%2FmzMd4evRg9yDi@fedora/
Cc: Hillf Danton <hdanton@sina.com>
Cc: Yu Kuai <yukuai3@huawei.com>
Cc: Dennis Zhou <dennis@kernel.org>
Fixes: 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of percpu_ref in fast path")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20221215021629.74870-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Saranya Muruganandam <saranyamohan@google.com>
---
 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