diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 29f9ac8817d7b0eff91d7d9fd2292af6804b445a..a5e3ee28006f9fc1383a918fe86dacdf2c09d45b 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1808,11 +1808,11 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs)
 	disk->major = NBD_MAJOR;
 
 	/* Too big first_minor can cause duplicate creation of
-	 * sysfs files/links, since MKDEV() expect that the max bits of
-	 * first_minor is 20.
+	 * sysfs files/links, since index << part_shift might overflow, or
+	 * MKDEV() expect that the max bits of first_minor is 20.
 	 */
 	disk->first_minor = index << part_shift;
-	if (disk->first_minor > MINORMASK) {
+	if (disk->first_minor < index || disk->first_minor > MINORMASK) {
 		err = -EINVAL;
 		goto out_free_idr;
 	}