linux-kernel - [PATCH 4.19 02/24] block: fix NULL pointer dereference in register

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Date:   Thu, 11 Feb 2021 16:02:36 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, zhengbin <zhengbin13@...wei.com>,
        Jens Axboe <axboe@...nel.dk>,
        Jack Wang <jinpu.wang@...ud.ionos.com>
Subject: [PATCH 4.19 02/24] block: fix NULL pointer dereference in register_disk

From: zhengbin <zhengbin13@...wei.com>

commit 4d7c1d3fd7c7eda7dea351f071945e843a46c145 upstream.

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@...wei.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Jack Wang <jinpu.wang@...ud.ionos.com>
---
 block/genhd.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/block/genhd.c
+++ b/block/genhd.c
@@ -652,10 +652,12 @@ 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);
+	}
 }
 
 /**