From: zhengbin <zhengbin13@huawei.com>
Date: Wed, 20 Feb 2019 13:27:05 +0000 (+0800)
Subject: block: fix NULL pointer dereference in register_disk
X-Git-Tag: v5.1-rc1~100^2~5
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=4d7c1d3fd7c7eda7dea351f071945e843a46c145;p=linux.git

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 1dd8fd6613b8..78b82d26aa9c 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -655,10 +655,12 @@ static void register_disk(struct device *parent, struct gendisk *disk,
 		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);
+	}
 }
 
 /**