netfilter: nft_nat: insufficient attribute validation

We have to validate that we at least get an NFTA_NAT_REG_ADDR_MIN or
NFTA_NFT_REG_PROTO_MIN attribute. Reject the configuration if none
of them are present.
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nft_nat.c

@@ -99,7 +99,9 @@ static int nft_nat_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
 	if (err < 0)
 		return err;
 
-	if (tb[NFTA_NAT_TYPE] == NULL)
+	if (tb[NFTA_NAT_TYPE] == NULL ||
+	    (tb[NFTA_NAT_REG_ADDR_MIN] == NULL &&
+	     tb[NFTA_NAT_REG_PROTO_MIN] == NULL))
 		return -EINVAL;
 
 	switch (ntohl(nla_get_be32(tb[NFTA_NAT_TYPE]))) {