Re: [PATCH V5 6/9] blk-mq: always free hctx after request queue is freed

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 4/12/19 5:30 AM, Ming Lei wrote:
In normal queue cleanup path, hctx is released after request queue
is freed, see blk_mq_release().

However, in __blk_mq_update_nr_hw_queues(), hctx may be freed because
of hw queues shrinking. This way is easy to cause use-after-free,
because: one implicit rule is that it is safe to call almost all block
layer APIs if the request queue is alive; and one hctx may be retrieved
by one API, then the hctx can be freed by blk_mq_update_nr_hw_queues();
finally use-after-free is triggered.

Fixes this issue by always freeing hctx after releasing request queue.
If some hctxs are removed in blk_mq_update_nr_hw_queues(), introduce
a per-queue list to hold them, then try to resuse these hctxs if numa
node is matched.

Cc: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
Cc: James Smart <james.smart@xxxxxxxxxxxx>
Cc: Bart Van Assche <bart.vanassche@xxxxxxx>
Cc: linux-scsi@xxxxxxxxxxxxxxx,
Cc: Martin K . Petersen <martin.petersen@xxxxxxxxxx>,
Cc: Christoph Hellwig <hch@xxxxxx>,
Cc: James E . J . Bottomley <jejb@xxxxxxxxxxxxxxxxxx>,
Cc: jianchao wang <jianchao.w.wang@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
  block/blk-mq.c         | 40 +++++++++++++++++++++++++++-------------
  include/linux/blk-mq.h |  2 ++
  include/linux/blkdev.h |  7 +++++++
  3 files changed, 36 insertions(+), 13 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 71996fe494eb..886fbb678617 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2260,6 +2260,10 @@ static void blk_mq_exit_hctx(struct request_queue *q,
  		set->ops->exit_hctx(hctx, hctx_idx);
blk_mq_remove_cpuhp(hctx);
+
+	spin_lock(&q->dead_hctx_lock);
+	list_add(&hctx->hctx_list, &q->dead_hctx_list);
+	spin_unlock(&q->dead_hctx_lock);
  }
static void blk_mq_exit_hw_queues(struct request_queue *q,
@@ -2660,15 +2664,13 @@ static int blk_mq_alloc_ctxs(struct request_queue *q)
   */
  void blk_mq_release(struct request_queue *q)
  {
-	struct blk_mq_hw_ctx *hctx;
-	unsigned int i;
+	struct blk_mq_hw_ctx *hctx, *next;
cancel_delayed_work_sync(&q->requeue_work); - /* hctx kobj stays in hctx */
-	queue_for_each_hw_ctx(q, hctx, i) {
-		if (!hctx)
-			continue;
+	/* all hctx are in .dead_hctx_list now */
+	list_for_each_entry_safe(hctx, next, &q->dead_hctx_list, hctx_list) {
+		list_del_init(&hctx->hctx_list);
  		kobject_put(&hctx->kobj);
  	}
@@ -2735,9 +2737,22 @@ static struct blk_mq_hw_ctx *blk_mq_alloc_and_init_hctx(
  		struct blk_mq_tag_set *set, struct request_queue *q,
  		int hctx_idx, int node)
  {
-	struct blk_mq_hw_ctx *hctx;
+	struct blk_mq_hw_ctx *hctx = NULL, *tmp;
+
+	/* reuse dead hctx first */
+	spin_lock(&q->dead_hctx_lock);
+	list_for_each_entry(tmp, &q->dead_hctx_list, hctx_list) {
+		if (tmp->numa_node == node) {
+			hctx = tmp;
+			break;
+		}
+	}
+	if (hctx)
+		list_del_init(&hctx->hctx_list);
+	spin_unlock(&q->dead_hctx_lock);
- hctx = blk_mq_alloc_hctx(q, set, hctx_idx, node);
+	if (!hctx)
+		hctx = blk_mq_alloc_hctx(q, set, hctx_idx, node);
  	if (!hctx)
  		goto fail;
@@ -2775,10 +2790,8 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, hctx = blk_mq_alloc_and_init_hctx(set, q, i, node);
  		if (hctx) {
-			if (hctxs[i]) {
+			if (hctxs[i])
  				blk_mq_exit_hctx(q, set, hctxs[i], i);
-				kobject_put(&hctxs[i]->kobj);
-			}
  			hctxs[i] = hctx;
  		} else {
  			if (hctxs[i])
@@ -2809,9 +2822,7 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
  			if (hctx->tags)
  				blk_mq_free_map_and_requests(set, j);
  			blk_mq_exit_hctx(q, set, hctx, j);
-			kobject_put(&hctx->kobj);
  			hctxs[j] = NULL;
-
  		}
  	}
  	mutex_unlock(&q->sysfs_lock);
@@ -2854,6 +2865,9 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
  	if (!q->queue_hw_ctx)
  		goto err_sys_init;
+ INIT_LIST_HEAD(&q->dead_hctx_list);
+	spin_lock_init(&q->dead_hctx_lock);
+
  	blk_mq_realloc_hw_ctxs(set, q);
  	if (!q->nr_hw_queues)
  		goto err_hctxs;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index cb2aa7ecafff..a44c3f95dcc1 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -70,6 +70,8 @@ struct blk_mq_hw_ctx {
  	struct dentry		*sched_debugfs_dir;
  #endif
+ struct list_head hctx_list;
+
  	/* Must be the last member - see also blk_mq_hw_ctx_size(). */
  	struct srcu_struct	srcu[0];
  };
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 4b85dc066264..1325f941f0be 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -535,6 +535,13 @@ struct request_queue {
struct mutex sysfs_lock; + /*
+	 * for reusing dead hctx instance in case of updating
+	 * nr_hw_queues
+	 */
+	struct list_head	dead_hctx_list;
+	spinlock_t		dead_hctx_lock;
+
  	atomic_t		mq_freeze_depth;
#if defined(CONFIG_BLK_DEV_BSG)

I actually had been looking into this, too, but couldn't convince myself that the code really is a problem.
Did you see this happening in real life?

Cheers,

Hannes
--
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@xxxxxxx			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG Nürnberg)



[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [SCSI Target Devel]     [Linux SCSI Target Infrastructure]     [Kernel Newbies]     [IDE]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux ATA RAID]     [Linux IIO]     [Samba]     [Device Mapper]

  Powered by Linux