Messages in this thread Patch in this message | | | From | Sasha Levin <> | Subject | [PATCH AUTOSEL 6.4 10/15] blk-mq: fix NULL dereference on q->elevator in blk_mq_elv_switch_none | Date | Sun, 2 Jul 2023 15:40:15 -0400 |
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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; -- 2.39.2
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