net: Handle unregister properly when netdev namespace change fails.

If rtnl_newlink() fails on it's call to dev_change_net_namespace(), we
have to make use of the ->dellink() method, if present, just like we
do when rtnl_configure_link() fails.

Fixes: 317f4810 ("rtnl: allow to create device with IFLA_LINK_NETNSID set")
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -2166,28 +2166,28 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh)
 			}
 		}
 		err = rtnl_configure_link(dev, ifm);
-		if (err < 0) {
-			if (ops->newlink) {
-				LIST_HEAD(list_kill);
-
-				ops->dellink(dev, &list_kill);
-				unregister_netdevice_many(&list_kill);
-			} else {
-				unregister_netdevice(dev);
-			}
-			goto out;
-		}
-
+		if (err < 0)
+			goto out_unregister;
 		if (link_net) {
 			err = dev_change_net_namespace(dev, dest_net, ifname);
 			if (err < 0)
-				unregister_netdevice(dev);
+				goto out_unregister;
 		}
 out:
 		if (link_net)
 			put_net(link_net);
 		put_net(dest_net);
 		return err;
+out_unregister:
+		if (ops->newlink) {
+			LIST_HEAD(list_kill);
+
+			ops->dellink(dev, &list_kill);
+			unregister_netdevice_many(&list_kill);
+		} else {
+			unregister_netdevice(dev);
+		}
+		goto out;
 	}
 }