block: fix NULL pointer dereference in register_disk

If __device_add_disk-->bdi_register_owner-->bdi_register-->
bdi_register_va-->device_create_vargs fails, bdi->dev is still
NULL, __device_add_disk-->register_disk will visit bdi->dev->kobj.
This patch fixes that.

Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/genhd.c b/block/genhd.c
index 1dd8fd6..78b82d2 100644 (file)
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -655,10 +655,12 @@ exit:
                kobject_uevent(&part_to_dev(part)->kobj, KOBJ_ADD);
        disk_part_iter_exit(&piter);
 
-       err = sysfs_create_link(&ddev->kobj,
-                               &disk->queue->backing_dev_info->dev->kobj,
-                               "bdi");
-       WARN_ON(err);
+       if (disk->queue->backing_dev_info->dev) {
+               err = sysfs_create_link(&ddev->kobj,
+                         &disk->queue->backing_dev_info->dev->kobj,
+                         "bdi");
+               WARN_ON(err);
+       }
 }
 
 /**