net: Fix incorrect address comparison when searching for a bind2 bucket

The v6_rcv_saddr and rcv_saddr are inside a union in the
'struct inet_bind2_bucket'.  When searching a bucket by following the
bhash2 hashtable chain, eg. inet_bind2_bucket_match, it is only using
the sk->sk_family and there is no way to check if the inet_bind2_bucket
has a v6 or v4 address in the union.  This leads to an uninit-value
KMSAN report in [0] and also potentially incorrect matches.

This patch fixes it by adding a family member to the inet_bind2_bucket
and then tests 'sk->sk_family != tb->family' before matching
the sk's address to the tb's address.

Cc: Joanne Koong <joannelkoong@gmail.com>
Fixes: 28044fc ("net: Add a bhash2 table hashed by port and address")
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Tested-by: Alexander Potapenko <glider@google.com>
Link: https://lore.kernel.org/r/20220927002544.3381205-1-kafai@fb.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Martin KaFai Lau

include/net/inet_hashtables.h

@@ -95,6 +95,9 @@ struct inet_bind2_bucket {
 	possible_net_t		ib_net;
 	int			l3mdev;
 	unsigned short		port;
+#if IS_ENABLED(CONFIG_IPV6)
+	unsigned short		family;
+#endif
 	union {
 #if IS_ENABLED(CONFIG_IPV6)
 		struct in6_addr		v6_rcv_saddr;

net/ipv4/inet_hashtables.c

@@ -109,6 +109,7 @@ static void inet_bind2_bucket_init(struct inet_bind2_bucket *tb,
 	tb->l3mdev    = l3mdev;
 	tb->port      = port;
 #if IS_ENABLED(CONFIG_IPV6)
+	tb->family    = sk->sk_family;
 	if (sk->sk_family == AF_INET6)
 		tb->v6_rcv_saddr = sk->sk_v6_rcv_saddr;
 	else
@@ -146,6 +147,9 @@ static bool inet_bind2_bucket_addr_match(const struct inet_bind2_bucket *tb2,
 					 const struct sock *sk)
 {
 #if IS_ENABLED(CONFIG_IPV6)
+	if (sk->sk_family != tb2->family)
+		return false;
+
 	if (sk->sk_family == AF_INET6)
 		return ipv6_addr_equal(&tb2->v6_rcv_saddr,
 				       &sk->sk_v6_rcv_saddr);
@@ -791,6 +795,9 @@ static bool inet_bind2_bucket_match(const struct inet_bind2_bucket *tb,
 				    int l3mdev, const struct sock *sk)
 {
 #if IS_ENABLED(CONFIG_IPV6)
+	if (sk->sk_family != tb->family)
+		return false;
+
 	if (sk->sk_family == AF_INET6)
 		return net_eq(ib2_net(tb), net) && tb->port == port &&
 			tb->l3mdev == l3mdev &&
@@ -807,6 +814,9 @@ bool inet_bind2_bucket_match_addr_any(const struct inet_bind2_bucket *tb, const
 #if IS_ENABLED(CONFIG_IPV6)
 	struct in6_addr addr_any = {};
 
+	if (sk->sk_family != tb->family)
+		return false;
+
 	if (sk->sk_family == AF_INET6)
 		return net_eq(ib2_net(tb), net) && tb->port == port &&
 			tb->l3mdev == l3mdev &&