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authorMing Lei <ming.lei@redhat.com>2019-04-30 09:52:27 +0800
committerJens Axboe <axboe@kernel.dk>2019-05-04 07:24:08 -0600
commit2f8f1336a48bd5186de3476da0a3e2ec06d0533a (patch)
tree1bc1ee8510442e16f00ba1cf82ebfb0dfb926017 /block
parent7c6c5b7c9186e3fb5b10afb8e5f710ae661144c6 (diff)
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blk-mq: always free hctx after request queue is freed
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@oracle.com> Cc: James Smart <james.smart@broadcom.com> Cc: Bart Van Assche <bart.vanassche@wdc.com> Cc: linux-scsi@vger.kernel.org, Cc: Martin K . Petersen <martin.petersen@oracle.com>, Cc: Christoph Hellwig <hch@lst.de>, Cc: James E . J . Bottomley <jejb@linux.vnet.ibm.com>, Reviewed-by: Hannes Reinecke <hare@suse.com> Tested-by: James Smart <james.smart@broadcom.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/blk-mq.c46
1 files changed, 33 insertions, 13 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 17e63d80b6d6..08a6248d8536 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2269,6 +2269,10 @@ 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,
@@ -2351,6 +2355,8 @@ blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
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
@@ -2664,15 +2670,17 @@ 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);
}
@@ -2739,9 +2747,22 @@ 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, 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, node);
if (!hctx)
goto fail;
@@ -2779,10 +2800,8 @@ 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])
@@ -2813,9 +2832,7 @@ 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);
@@ -2858,6 +2875,9 @@ 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;