diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index b1a5acd57426..7ec85f94f742 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1278,6 +1278,13 @@ static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
 	/* Arg will be cast to int, check it to avoid overflow */
 	if (arg > INT_MAX)
 		return -EINVAL;
+
+	if (nbd->pid) {
+		dev_err(disk_to_dev(nbd->disk),
+			"Cannot add socket to a running device\n");
+		return -EBUSY;
+	}
+
 	sock = nbd_get_socket(nbd, arg, &err);
 	if (!sock)
 		return err;