From: Ming Lei ming.lei@redhat.com
[ Upstream commit 245165658e1c9f95c0fecfe02b9b1ebd30a1198a ]
After grabbing q->sysfs_lock, q->elevator may become NULL because of elevator switch.
Fix the NULL dereference on q->elevator by checking it with lock.
Reported-by: Guangwu Zhang guazhang@redhat.com Signed-off-by: Ming Lei ming.lei@redhat.com Link: https://lore.kernel.org/r/20230616132354.415109-1-ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- block/blk-mq.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c index 850bfb844ed2f..9516f65a50ea4 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -4608,9 +4608,6 @@ static bool blk_mq_elv_switch_none(struct list_head *head, { struct blk_mq_qe_pair *qe;
- if (!q->elevator) - return true; - qe = kmalloc(sizeof(*qe), GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY); if (!qe) return false; @@ -4618,6 +4615,12 @@ static bool blk_mq_elv_switch_none(struct list_head *head, /* q->elevator needs protection from ->sysfs_lock */ mutex_lock(&q->sysfs_lock);
+ /* the check has to be done with holding sysfs_lock */ + if (!q->elevator) { + kfree(qe); + goto unlock; + } + INIT_LIST_HEAD(&qe->node); qe->q = q; qe->type = q->elevator->type; @@ -4625,6 +4628,7 @@ static bool blk_mq_elv_switch_none(struct list_head *head, __elevator_get(qe->type); list_add(&qe->node, head); elevator_disable(q); +unlock: mutex_unlock(&q->sysfs_lock);
return true;