From: Ming Lei ming.lei@redhat.com
[ Upstream commit 5fd7a84a09e640016fe106dd3e992f5210e23dc7 ]
elevator can be tore down by sysfs switch interface or disk release, so hold ->sysfs_lock before referring to q->elevator, then potential use-after-free can be avoided.
Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Ming Lei ming.lei@redhat.com Link: https://lore.kernel.org/r/20220616014401.817001-2-ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- block/blk-mq.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c index f18e1c9c3f4a..5021e8ed2053 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -4433,12 +4433,14 @@ static bool blk_mq_elv_switch_none(struct list_head *head, if (!qe) return false;
+ /* q->elevator needs protection from ->sysfs_lock */ + mutex_lock(&q->sysfs_lock); + INIT_LIST_HEAD(&qe->node); qe->q = q; qe->type = q->elevator->type; list_add(&qe->node, head);
- mutex_lock(&q->sysfs_lock); /* * After elevator_switch_mq, the previous elevator_queue will be * released by elevator_release. The reference of the io scheduler