netfilter: nf_tables: disallow element updates of bound anonymous sets

Anonymous sets come with NFT_SET_CONSTANT from userspace. Although API
allows to create anonymous sets without NFT_SET_CONSTANT, it makes no
sense to allow to add and to delete elements for bound anonymous sets.

Fixes: 96518518 ("netfilter: add nftables")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -6779,7 +6779,8 @@ static int nf_tables_newsetelem(struct sk_buff *skb,
 	if (IS_ERR(set))
 		return PTR_ERR(set);
 
-	if (!list_empty(&set->bindings) && set->flags & NFT_SET_CONSTANT)
+	if (!list_empty(&set->bindings) &&
+	    (set->flags & (NFT_SET_CONSTANT | NFT_SET_ANONYMOUS)))
 		return -EBUSY;
 
 	nft_ctx_init(&ctx, net, skb, info->nlh, family, table, NULL, nla);
@@ -7053,7 +7054,9 @@ static int nf_tables_delsetelem(struct sk_buff *skb,
 	set = nft_set_lookup(table, nla[NFTA_SET_ELEM_LIST_SET], genmask);
 	if (IS_ERR(set))
 		return PTR_ERR(set);
-	if (!list_empty(&set->bindings) && set->flags & NFT_SET_CONSTANT)
+
+	if (!list_empty(&set->bindings) &&
+	    (set->flags & (NFT_SET_CONSTANT | NFT_SET_ANONYMOUS)))
 		return -EBUSY;
 
 	nft_ctx_init(&ctx, net, skb, info->nlh, family, table, NULL, nla);