netfilter: nft_set_pipapo: .walk does not deal with generations

jira VULN-430
cve-pre CVE-2023-4244
commit-author Pablo Neira Ayuso <pablo@netfilter.org>
commit 2b84e21

The .walk callback iterates over the current active set, but it might be
useful to iterate over the next generation set. Use the generation mask
to determine what set view (either current or next generation) is use
for the walk iteration.

Fixes: 3c4287f ("nf_tables: Add set type for arbitrary concatenation of ranges")
	Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
(cherry picked from commit 2b84e21)
	Signed-off-by: Marcin Wcisło <marcin.wcislo@conclusive.pl>

Author: pvts-mat

net/netfilter/nft_set_pipapo.c

@@ -1978,12 +1978,16 @@ static void nft_pipapo_walk(const struct nft_ctx *ctx, struct nft_set *set,
 			    struct nft_set_iter *iter)
 {
 	struct nft_pipapo *priv = nft_set_priv(set);
+	struct net *net = read_pnet(&set->net);
 	struct nft_pipapo_match *m;
 	struct nft_pipapo_field *f;
 	int i, r;
 
 	rcu_read_lock();
-	m = rcu_dereference(priv->match);
+	if (iter->genmask == nft_genmask_cur(net))
+		m = rcu_dereference(priv->match);
+	else
+		m = priv->clone;
 
 	if (unlikely(!m))
 		goto out;