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>,
Tested-by: James Smart <james.smart@xxxxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/blk-mq.c | 46 +++++++++++++++++++++++++++++++++-------------
include/linux/blk-mq.h | 2 ++
include/linux/blkdev.h | 7 +++++++
3 files changed, 42 insertions(+), 13 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 1eceeb26ae7d..b9d711d12cae 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2274,6 +2274,10 @@ 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->unused_hctx_lock);
+ list_add(&hctx->hctx_list, &q->unused_hctx_list);
+ spin_unlock(&q->unused_hctx_lock);
}
static void blk_mq_exit_hw_queues(struct request_queue *q,
@@ -2362,6 +2366,8 @@ blk_mq_alloc_hctx(struct request_queue *q,
hctx->queue = q;
hctx->flags = set->flags & ~BLK_MQ_F_TAG_SHARED;
+ INIT_LIST_HEAD(&hctx->hctx_list);
+
/*
* Allocate space for all possible cpus to avoid allocation at
* runtime
@@ -2675,15 +2681,17 @@ 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;
+ int i;
cancel_delayed_work_sync(&q->requeue_work);
- /* hctx kobj stays in hctx */
- queue_for_each_hw_ctx(q, hctx, i) {
- if (!hctx)
- continue;
+ queue_for_each_hw_ctx(q, hctx, i)
+ WARN_ON_ONCE(hctx && list_empty(&hctx->hctx_list));
+
+ /* all hctx are in .unused_hctx_list now */
+ list_for_each_entry_safe(hctx, next, &q->unused_hctx_list, hctx_list) {
+ list_del_init(&hctx->hctx_list);
kobject_put(&hctx->kobj);
}
@@ -2750,9 +2758,22 @@ 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;
- hctx = blk_mq_alloc_hctx(q, set, hctx_idx, node);
+ /* reuse dead hctx first */
+ spin_lock(&q->unused_hctx_lock);
+ list_for_each_entry(tmp, &q->unused_hctx_list, hctx_list) {
+ if (tmp->numa_node == node) {
+ hctx = tmp;
+ break;
+ }
+ }
+ if (hctx)
+ list_del_init(&hctx->hctx_list);
+ spin_unlock(&q->unused_hctx_lock);
+
+ if (!hctx)
+ hctx = blk_mq_alloc_hctx(q, set, hctx_idx, node);
if (!hctx)
goto fail;
@@ -2790,10 +2811,8 @@ 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])
@@ -2824,9 +2843,7 @@ 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);
@@ -2869,6 +2886,9 @@ 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->unused_hctx_list);
+ spin_lock_init(&q->unused_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 db29928de467..15d1aa53d96c 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 99aa98f60b9e..d7bad4ae8bc8 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 unused_hctx_list;
+ spinlock_t unused_hctx_lock;
+
atomic_t mq_freeze_depth;
#if defined(CONFIG_BLK_DEV_BSG)
--
2.9.5
