net/mlx5: fs, assert null dest pointer when dest_num is 0

Currently create_flow_handle() assumes a null dest pointer when there
are no destinations.
This might not be the case as the caller may pass an allocated dest
array while setting the dest_num parameter to 0.

Assert null dest array for flow rules that have no destinations (e.g. drop
rule).
Signed-off-by: Oz Shlomo <ozsh@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Link: https://lore.kernel.org/r/20221203221337.29267-3-saeed@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mellanox/mlx5/core/fs_core.c

@@ -1962,6 +1962,9 @@ _mlx5_add_flow_rules(struct mlx5_flow_table *ft,
 	if (flow_act->fg && ft->autogroup.active)
 		return ERR_PTR(-EINVAL);
 
+	if (dest && dest_num <= 0)
+		return ERR_PTR(-EINVAL);
+
 	for (i = 0; i < dest_num; i++) {
 		if (!dest_is_valid(&dest[i], flow_act, ft))
 			return ERR_PTR(-EINVAL);