[PATCH 3/4] block: Make del_gendisk() safer for disks without queues

Jan Kara
2017-03-09T10:16:23Z

Commit 165a5e22fafb "block: Move bdi_unregister() to del_gendisk()"
added disk->queue dereference to del_gendisk(). Although del_gendisk()
is not supposed to be called without disk->queue valid and
blk_unregister_queue() warns in that case, this change will make it oops
instead. Return to the old more robust behavior of just warning when
del_gendisk() gets called for gendisk with disk->queue being NULL.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Tested-by: Omar Sandoval <osandov@fb.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
---
block/genhd.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index b26a5ea115d0..94f323842b52 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -681,12 +681,16 @@ void del_gendisk(struct gendisk *disk)
disk->flags &= ~GENHD_FL_UP;

sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");
- /*
- * Unregister bdi before releasing device numbers (as they can get
- * reused and we'd get clashes in sysfs).
- */
- bdi_unregister(disk->queue->backing_dev_info);
- blk_unregister_queue(disk);
+ if (disk->queue) {
+ /*
+ * Unregister bdi before releasing device numbers (as they can
+ * get reused and we'd get clashes in sysfs).
+ */
+ bdi_unregister(disk->queue->backing_dev_info);
+ blk_unregister_queue(disk);
+ } else {
+ WARN_ON(1);
+ }
blk_unregister_region(disk_devt(disk), disk->minors);

part_stat_set_all(&disk->part0, 0);
--
2.10.2