block: disable the elevator int del_gendisk
The elevator is only used for file system requests, which are stopped in
del_gendisk. Move disabling the elevator and freeing the scheduler tags
to the end of del_gendisk instead of doing that work in disk_release and
blk_cleanup_queue to avoid a use after free on q->tag_set from
disk_release as the tag_set might not be alive at that point.
Move the blk_qos_exit call as well, as it just depends on the elevator
exit and would be the only reason to keep the not exactly cheap queue
freeze in disk_release.
Fixes: e155b0c238b2 ("blk-mq: Use shared tags for shared sbitmap support")
Reported-by: syzbot+3e3f419f4a7816471838@syzkaller.appspotmail.com
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: syzbot+3e3f419f4a7816471838@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/20220614074827.458955-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/genhd.c b/block/genhd.c
index 27205ae..e067577 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -652,6 +652,17 @@ void del_gendisk(struct gendisk *disk)
blk_sync_queue(q);
blk_flush_integrity();
+ blk_mq_cancel_work_sync(q);
+
+ blk_mq_quiesce_queue(q);
+ if (q->elevator) {
+ mutex_lock(&q->sysfs_lock);
+ elevator_exit(q);
+ mutex_unlock(&q->sysfs_lock);
+ }
+ rq_qos_exit(q);
+ blk_mq_unquiesce_queue(q);
+
/*
* Allow using passthrough request again after the queue is torn down.
*/
@@ -1120,31 +1131,6 @@ static const struct attribute_group *disk_attr_groups[] = {
NULL
};
-static void disk_release_mq(struct request_queue *q)
-{
- blk_mq_cancel_work_sync(q);
-
- /*
- * There can't be any non non-passthrough bios in flight here, but
- * requests stay around longer, including passthrough ones so we
- * still need to freeze the queue here.
- */
- blk_mq_freeze_queue(q);
-
- /*
- * Since the I/O scheduler exit code may access cgroup information,
- * perform I/O scheduler exit before disassociating from the block
- * cgroup controller.
- */
- if (q->elevator) {
- mutex_lock(&q->sysfs_lock);
- elevator_exit(q);
- mutex_unlock(&q->sysfs_lock);
- }
- rq_qos_exit(q);
- __blk_mq_unfreeze_queue(q, true);
-}
-
/**
* disk_release - releases all allocated resources of the gendisk
* @dev: the device representing this disk
@@ -1166,9 +1152,6 @@ static void disk_release(struct device *dev)
might_sleep();
WARN_ON_ONCE(disk_live(disk));
- if (queue_is_mq(disk->queue))
- disk_release_mq(disk->queue);
-
blkcg_exit_queue(disk->queue);
disk_release_events(disk);
