tcp: Fix bind() conflict check for dual-stack wildcard address.

Paul Holzinger reported [0] that commit 5456262d ("net: Fix
incorrect address comparison when searching for a bind2 bucket")
introduced a bind() regression.  Paul also gave a nice repro that
calls two types of bind() on the same port, both of which now
succeed, but the second call should fail:

  bind(fd1, ::, port) + bind(fd2, 127.0.0.1, port)

The cited commit added address family tests in three functions to
fix the uninit-value KMSAN report. [1]  However, the test added to
inet_bind2_bucket_match_addr_any() removed a necessary conflict
check; the dual-stack wildcard address no longer conflicts with
an IPv4 non-wildcard address.

If tb->family is AF_INET6 and sk->sk_family is AF_INET in
inet_bind2_bucket_match_addr_any(), we still need to check
if tb has the dual-stack wildcard address.

Note that the IPv4 wildcard address does not conflict with
IPv6 non-wildcard addresses.

[0]: https://lore.kernel.org/netdev/e21bf153-80b0-9ec0-15ba-e04a4ad42c34@redhat.com/
[1]: https://lore.kernel.org/netdev/CAG_fn=Ud3zSW7AZWXc+asfMhZVL5ETnvuY44Pmyv4NPv-ijN-A@mail.gmail.com/

Fixes: 5456262d ("net: Fix incorrect address comparison when searching for a bind2 bucket")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reported-by: Paul Holzinger <pholzing@redhat.com>
Link: https://lore.kernel.org/netdev/CAG_fn=Ud3zSW7AZWXc+asfMhZVL5ETnvuY44Pmyv4NPv-ijN-A@mail.gmail.com/Reviewed-by: Eric Dumazet <edumazet@google.com>
Tested-by: Paul Holzinger <pholzing@redhat.com>
Reviewed-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/inet_hashtables.c

@@ -828,8 +828,14 @@ 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)
+	if (sk->sk_family != tb->family) {
+		if (sk->sk_family == AF_INET)
+			return net_eq(ib2_net(tb), net) && tb->port == port &&
+				tb->l3mdev == l3mdev &&
+				ipv6_addr_equal(&tb->v6_rcv_saddr, &addr_any);
+
 		return false;
+	}
 
 	if (sk->sk_family == AF_INET6)
 		return net_eq(ib2_net(tb), net) && tb->port == port &&