block/elevator: handle possible null pointer

[PATCH] block/elevator: handle possible null pointer

Posted by Peng Hao 4 years, 6 months ago

There is a check for q->tag_set in the front of elevator_get_default,
and there should be a check here too.

Signed-off-by: Peng Hao <flyingpeng@tencent.com>
---
 block/elevator.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/elevator.c b/block/elevator.c
index 1f39f6e8ebb9..b7d0bead680c 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -636,7 +636,7 @@ static struct elevator_type *elevator_get_default(struct request_queue *q)
 	if (q->tag_set && q->tag_set->flags & BLK_MQ_F_NO_SCHED_BY_DEFAULT)
 		return NULL;
 
-	if (q->nr_hw_queues != 1 &&
+	if (q->nr_hw_queues != 1 && q->tag_set &&
 	    !blk_mq_is_shared_tags(q->tag_set->flags))
 		return NULL;
 
-- 
2.27.0

Re: [PATCH] block/elevator: handle possible null pointer

Posted by Jens Axboe 4 years, 6 months ago

On 12/21/21 1:10 AM, Peng Hao wrote:
> There is a check for q->tag_set in the front of elevator_get_default,
> and there should be a check here too.

I always get suspicious when I see patches like that. Is the other check
valid? Why does it need to get checked? There's really no meat on the
bone in this commit message.

-- 
Jens Axboe