diff --git a/sys/dev/mlx5/mlx5_ib/mlx5_ib_main.c b/sys/dev/mlx5/mlx5_ib/mlx5_ib_main.c
--- a/sys/dev/mlx5/mlx5_ib/mlx5_ib_main.c
+++ b/sys/dev/mlx5/mlx5_ib/mlx5_ib_main.c
@@ -2499,11 +2499,14 @@
 	struct mlx5_ib_flow_prio *ft_prio;
 	int err;
 
+	if (udata &&
+	    udata->inlen && !ib_is_udata_cleared(udata, 0, udata->inlen))
+		return ERR_PTR(-EOPNOTSUPP);
+
 	if (flow_attr->priority > MLX5_IB_FLOW_LAST_PRIO)
 		return ERR_PTR(-ENOSPC);
 
 	if (domain != IB_FLOW_DOMAIN_USER ||
-	    udata != NULL ||
 	    flow_attr->port > MLX5_CAP_GEN(dev->mdev, num_ports) ||
 	    (flow_attr->flags & ~IB_FLOW_ATTR_FLAGS_DONT_TRAP))
 		return ERR_PTR(-EINVAL);