linux-kernel - [PATCH] block/elevator: handle possible null pointer

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Message-Id: <20211221081042.78799-1-flyingpeng@tencent.com>
Date:   Tue, 21 Dec 2021 16:10:42 +0800
From:   Peng Hao <flyingpenghao@...il.com>
To:     axboe@...nel.dk
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH]  block/elevator: handle possible null pointer

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@...cent.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