The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e26cc08265dda37d2acc8394604f220ef412299d Mon Sep 17 00:00:00 2001

From: zhengbin zhengbin13@huawei.com Date: Mon, 12 Aug 2019 20:36:55 +0800 Subject: [PATCH] blk-mq: move cancel of requeue_work to the front of blk_exit_queue

blk_exit_queue will free elevator_data, while blk_mq_requeue_work will access it. Move cancel of requeue_work to the front of blk_exit_queue to avoid use-after-free.

blk_exit_queue blk_mq_requeue_work __elevator_exit blk_mq_run_hw_queues blk_mq_exit_sched blk_mq_run_hw_queue dd_exit_queue blk_mq_hctx_has_pending kfree(elevator_data) blk_mq_sched_has_work dd_has_work

Fixes: fbc2a15e3433 ("blk-mq: move cancel of requeue_work into blk_mq_release") Cc: stable@vger.kernel.org Reviewed-by: Ming Lei ming.lei@redhat.com Signed-off-by: zhengbin zhengbin13@huawei.com Signed-off-by: Jens Axboe axboe@kernel.dk

diff --git a/block/blk-mq.c b/block/blk-mq.c index f78d3287dd82..a8e6a58f5f28 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2666,8 +2666,6 @@ void blk_mq_release(struct request_queue *q) struct blk_mq_hw_ctx *hctx, *next; int i;

- cancel_delayed_work_sync(&q->requeue_work); - queue_for_each_hw_ctx(q, hctx, i) WARN_ON_ONCE(hctx && list_empty(&hctx->hctx_list));

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 977c659dcd18..9bfa3ea4ed63 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -892,6 +892,9 @@ static void __blk_release_queue(struct work_struct *work)

blk_free_queue_stats(q->stats);

+ if (queue_is_mq(q)) + cancel_delayed_work_sync(&q->requeue_work); + blk_exit_queue(q);

blk_queue_free_zone_bitmaps(q);