[SRU Focal 1/1] netfilter: nf_tables: Reject tables of unsupported family

[Thadeu Lima de Souza Cascardo]

From: Phil Sutter <phil at nwl.cc>

An nftables family is merely a hollow container, its family just a
number and such not reliant on compile-time options other than nftables
support itself. Add an artificial check so attempts at using a family
the kernel can't support fail as early as possible. This helps user
space detect kernels which lack e.g. NFPROTO_INET.

Signed-off-by: Phil Sutter <phil at nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
(backported from commit f1082dd31fe461d482d69da2a8eccfeb7bf07ac2)
[cascardo: context adjustment due to nf_tables_newtable signature]
CVE-2023-6040
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
---
 net/netfilter/nf_tables_api.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 0b795e77b6e0..cf13d19ccad1 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -947,6 +947,30 @@ static int nft_objname_hash_cmp(struct rhashtable_compare_arg *arg,
 	return strcmp(obj->key.name, k->name);
 }
 
+static bool nft_supported_family(u8 family)
+{
+	return false
+#ifdef CONFIG_NF_TABLES_INET
+		|| family == NFPROTO_INET
+#endif
+#ifdef CONFIG_NF_TABLES_IPV4
+		|| family == NFPROTO_IPV4
+#endif
+#ifdef CONFIG_NF_TABLES_ARP
+		|| family == NFPROTO_ARP
+#endif
+#ifdef CONFIG_NF_TABLES_NETDEV
+		|| family == NFPROTO_NETDEV
+#endif
+#if IS_ENABLED(CONFIG_NF_TABLES_BRIDGE)
+		|| family == NFPROTO_BRIDGE
+#endif
+#ifdef CONFIG_NF_TABLES_IPV6
+		|| family == NFPROTO_IPV6
+#endif
+		;
+}
+
 static int nf_tables_newtable(struct net *net, struct sock *nlsk,
 			      struct sk_buff *skb, const struct nlmsghdr *nlh,
 			      const struct nlattr * const nla[],
@@ -962,6 +986,9 @@ static int nf_tables_newtable(struct net *net, struct sock *nlsk,
 	struct nft_ctx ctx;
 	int err;
 
+	if (!nft_supported_family(family))
+		return -EOPNOTSUPP;
+
 	lockdep_assert_held(&nft_net->commit_mutex);
 	attr = nla[NFTA_TABLE_NAME];
 	table = nft_table_lookup(net, attr, family, genmask);
-- 
2.34.1