net: Check CHANGEUPPER notifier return value

switchdev drivers reflect the newly requested topology to hardware when
CHANGEUPPER is received, after software links were already formed.
However, the operation can fail and user will not be notified, as the
return value of the notifier is not checked.

Add this check and rollback software links if necessary.
Signed-off-by: NIdo Schimmel <idosch@mellanox.com>
Signed-off-by: NJiri Pirko <jiri@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -5490,8 +5490,12 @@ static int __netdev_upper_dev_link(struct net_device *dev,
 			goto rollback_lower_mesh;
 	}
 
-	call_netdevice_notifiers_info(NETDEV_CHANGEUPPER, dev,
-				      &changeupper_info.info);
+	ret = call_netdevice_notifiers_info(NETDEV_CHANGEUPPER, dev,
+					    &changeupper_info.info);
+	ret = notifier_to_errno(ret);
+	if (ret)
+		goto rollback_lower_mesh;
+
 	return 0;
 
 rollback_lower_mesh: