diff --git a/drivers/md/md.c b/drivers/md/md.c
index 118de338266a..03e35386a802 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -6404,12 +6404,22 @@ struct mddev *md_alloc(dev_t dev, char *name)
 
 	disk->events |= DISK_EVENT_MEDIA_CHANGE;
 	mddev->gendisk = disk;
+
+	/*
+	 * add_disk() makes the array openable before mddev->kobj exists.
+	 * Hold reconfig_mutex until kobject_add() is done so that ioctls
+	 * issued in between wait instead of using an uninitialised kobj.
+	 */
+	mddev_lock_nointr(mddev);
 	error = add_disk(disk);
-	if (error)
+	if (error) {
+		mddev_unlock(mddev);
 		goto out_put_disk;
+	}
 
 	kobject_init(&mddev->kobj, &md_ktype);
 	error = kobject_add(&mddev->kobj, &disk_to_dev(disk)->kobj, "%s", "md");
+	mddev_unlock(mddev);
 	if (error) {
 		/*
 		 * The disk is already live at this point.  Clear the hold flag