2020-10-09 08:07:32

by YangYang

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 <[email protected]>
---
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

2020-10-09 12:31:28

by Ming Lei

Subject: Re: [PATCH] blk-mq: move cancel of hctx->run_work to the front of blk_exit_queue

On Fri, Oct 09, 2020 at 01:00:14AM -0700, Yang Yang wrote:
> 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 <[email protected]>
> ---
> 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);
> + }
> +

Looks fine:

Reviewed-by: Ming Lei <[email protected]>

Thanks,
Ming

2020-10-09 20:00:20

by Jens Axboe

Subject: Re: [PATCH] blk-mq: move cancel of hctx->run_work to the front of blk_exit_queue

On 10/9/20 2:00 AM, Yang Yang wrote:
> 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.

Applied, thanks.

--
Jens Axboe