netfilter: nf_tables: reject destroy command to remove basechain hooks

Report EOPNOTSUPP if NFT_MSG_DESTROYCHAIN is used to delete hooks in an
existing netdev basechain, thus, only NFT_MSG_DELCHAIN is allowed.

Fixes: 7d937b10 ("netfilter: nf_tables: support for deleting devices in an existing netdev chain")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -2944,7 +2944,8 @@ static int nf_tables_delchain(struct sk_buff *skb, const struct nfnl_info *info,
 	nft_ctx_init(&ctx, net, skb, info->nlh, family, table, chain, nla);
 
 	if (nla[NFTA_CHAIN_HOOK]) {
-		if (chain->flags & NFT_CHAIN_HW_OFFLOAD)
+		if (NFNL_MSG_TYPE(info->nlh->nlmsg_type) == NFT_MSG_DESTROYCHAIN ||
+		    chain->flags & NFT_CHAIN_HW_OFFLOAD)
 			return -EOPNOTSUPP;
 
 		if (nft_is_base_chain(chain)) {