netfilter: nf_tables: reject NFT_SET_CONCAT with not field length description

It is still possible to set on the NFT_SET_CONCAT flag by specifying a
set size and no field description, report EINVAL in such case.

Fixes: 1b6345d4 ("netfilter: nf_tables: check NFT_SET_CONCAT flag if field_count is specified")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -5070,8 +5070,12 @@ static int nf_tables_newset(struct sk_buff *skb, const struct nfnl_info *info,
 		if (err < 0)
 			return err;
 
-		if (desc.field_count > 1 && !(flags & NFT_SET_CONCAT))
+		if (desc.field_count > 1) {
+			if (!(flags & NFT_SET_CONCAT))
+				return -EINVAL;
+		} else if (flags & NFT_SET_CONCAT) {
 			return -EINVAL;
+		}
 	} else if (flags & NFT_SET_CONCAT) {
 		return -EINVAL;
 	}