netfilter: nf_tables: __nft_expr_type_get() selects specific family type

In case that there are two types, prefer the family specify extension.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -2009,14 +2009,17 @@ EXPORT_SYMBOL_GPL(nft_unregister_expr);
 static const struct nft_expr_type *__nft_expr_type_get(u8 family,
 						       struct nlattr *nla)
 {
-	const struct nft_expr_type *type;
+	const struct nft_expr_type *type, *candidate = NULL;
 
 	list_for_each_entry(type, &nf_tables_expressions, list) {
-		if (!nla_strcmp(nla, type->name) &&
-		    (!type->family || type->family == family))
-			return type;
+		if (!nla_strcmp(nla, type->name)) {
+			if (!type->family && !candidate)
+				candidate = type;
+			else if (type->family == family)
+				candidate = type;
+		}
 	}
-	return NULL;
+	return candidate;
 }
 
 #ifdef CONFIG_MODULES