linux-kernel - [PATCH] blk-mq: move cancel of hctx->run_work to the front of blk_exit

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Message-Id: <20201009080015.3217-1-yang.yang@vivo.com>
Date:   Fri,  9 Oct 2020 01:00:14 -0700
From:   Yang Yang <yang.yang@...o.com>
To:     Jens Axboe <axboe@...nel.dk>, Bart Van Assche <bvanassche@....org>,
        Hannes Reinecke <hare@...e.com>,
        Ming Lei <ming.lei@...hat.com>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     onlyfever@...oud.com, yang.yang@...o.com
Subject: [PATCH] blk-mq: move cancel of hctx->run_work to the front of blk_exit_queue

blk_exit_queue will free elevator_data, while blk_mq_run_work_fn
will access it. Move cancel of hctx->run_work to the front of
blk_exit_queue to avoid use-after-free.

Fixes: 1b97871b501f ("blk-mq: move cancel of hctx->run_work into blk_mq_hw_sysfs_release")
Signed-off-by: Yang Yang <yang.yang@...o.com>
---
 block/blk-mq-sysfs.c | 2 --
 block/blk-sysfs.c    | 9 ++++++++-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 062229395a50..7b52e7657b2d 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -36,8 +36,6 @@ static void blk_mq_hw_sysfs_release(struct kobject *kobj)
 	struct blk_mq_hw_ctx *hctx = container_of(kobj, struct blk_mq_hw_ctx,
 						  kobj);
 
-	cancel_delayed_work_sync(&hctx->run_work);
-
 	if (hctx->flags & BLK_MQ_F_BLOCKING)
 		cleanup_srcu_struct(hctx->srcu);
 	blk_free_flush_queue(hctx->fq);
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 7dda709f3ccb..8c6bafc801dd 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -934,9 +934,16 @@ static void blk_release_queue(struct kobject *kobj)
 
 	blk_free_queue_stats(q->stats);
 
-	if (queue_is_mq(q))
+	if (queue_is_mq(q)) {
+		struct blk_mq_hw_ctx *hctx;
+		int i;
+
 		cancel_delayed_work_sync(&q->requeue_work);
 
+		queue_for_each_hw_ctx(q, hctx, i)
+			cancel_delayed_work_sync(&hctx->run_work);
+	}
+
 	blk_exit_queue(q);
 
 	blk_queue_free_zone_bitmaps(q);
-- 
2.17.1