netfilter: xtables: avoid NFPROTO_UNSPEC where needed

syzbot managed to call xt_cluster match via ebtables:

 WARNING: CPU: 0 PID: 11 at net/netfilter/xt_cluster.c:72 xt_cluster_mt+0x196/0x780
 [..]
 ebt_do_table+0x174b/0x2a40

Module registers to NFPROTO_UNSPEC, but it assumes ipv4/ipv6 packet
processing.  As this is only useful to restrict locally terminating
TCP/UDP traffic, register this for ipv4 and ipv6 family only.

Pablo points out that this is a general issue, direct users of the
set/getsockopt interface can call into targets/matches that were only
intended for use with ip(6)tables.

Check all UNSPEC matches and targets for similar issues:

- matches and targets are fine except if they assume skb_network_header()
  is valid -- this is only true when called from inet layer: ip(6) stack
  pulls the ip/ipv6 header into linear data area.
- targets that return XT_CONTINUE or other xtables verdicts must be
  restricted too, they are incompatbile with the ebtables traverser, e.g.
  EBT_CONTINUE is a completely different value than XT_CONTINUE.

Most matches/targets are changed to register for NFPROTO_IPV4/IPV6, as
they are provided for use by ip(6)tables.

The MARK target is also used by arptables, so register for NFPROTO_ARP too.

While at it, bail out if connbytes fails to enable the corresponding
conntrack family.

This change passes the selftests in iptables.git.

Reported-by: syzbot+256c348558aa5cf611a9@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netfilter-devel/66fec2e2.050a0220.9ec68.0047.GAE@google.com/
Fixes: 0269ea493734 ("netfilter: xtables: add cluster match")
Signed-off-by: Florian Westphal <fw@strlen.de>
Co-developed-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 23 insertions, 10 deletions

diff --git a/net/netfilter/xt_cluster.c b/net/netfilter/xt_cluster.c
index a047a545371e..908fd5f2c3c8 100644
--- a/net/netfilter/xt_cluster.c
+++ b/net/netfilter/xt_cluster.c
@@ -146,24 +146,37 @@ static void xt_cluster_mt_destroy(const struct xt_mtdtor_param *par)
 	nf_ct_netns_put(par->net, par->family);
 }
 
-static struct xt_match xt_cluster_match __read_mostly = {
-	.name		= "cluster",
-	.family		= NFPROTO_UNSPEC,
-	.match		= xt_cluster_mt,
-	.checkentry	= xt_cluster_mt_checkentry,
-	.matchsize	= sizeof(struct xt_cluster_match_info),
-	.destroy	= xt_cluster_mt_destroy,
-	.me		= THIS_MODULE,
+static struct xt_match xt_cluster_match[] __read_mostly = {
+	{
+		.name		= "cluster",
+		.family		= NFPROTO_IPV4,
+		.match		= xt_cluster_mt,
+		.checkentry	= xt_cluster_mt_checkentry,
+		.matchsize	= sizeof(struct xt_cluster_match_info),
+		.destroy	= xt_cluster_mt_destroy,
+		.me		= THIS_MODULE,
+	},
+#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
+	{
+		.name		= "cluster",
+		.family		= NFPROTO_IPV6,
+		.match		= xt_cluster_mt,
+		.checkentry	= xt_cluster_mt_checkentry,
+		.matchsize	= sizeof(struct xt_cluster_match_info),
+		.destroy	= xt_cluster_mt_destroy,
+		.me		= THIS_MODULE,
+	},
+#endif
 };
 
 static int __init xt_cluster_mt_init(void)
 {
-	return xt_register_match(&xt_cluster_match);
+	return xt_register_matches(xt_cluster_match, ARRAY_SIZE(xt_cluster_match));
 }
 
 static void __exit xt_cluster_mt_fini(void)
 {
-	xt_unregister_match(&xt_cluster_match);
+	xt_unregister_matches(xt_cluster_match, ARRAY_SIZE(xt_cluster_match));
 }
 
 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");