tcp: Fix bind() regression for v6-only wildcard and v4-mapped-v6 non-wildcard addresses.

Commit 5e07e672412b ("tcp: Use bhash2 for v4-mapped-v6 non-wildcard
address.") introduced bind() regression for v4-mapped-v6 address.

When we bind() the following two addresses on the same port, the 2nd
bind() should succeed but fails now.

  1. [::] w/ IPV6_ONLY
  2. ::ffff:127.0.0.1

After the chagne, v4-mapped-v6 uses bhash2 instead of bhash to
detect conflict faster, but I forgot to add a necessary change.

During the 2nd bind(), inet_bind2_bucket_match_addr_any() returns
the tb2 bucket of [::], and inet_bhash2_conflict() finally calls
inet_bind_conflict(), which returns true, meaning conflict.

  inet_bhash2_addr_any_conflict
  |- inet_bind2_bucket_match_addr_any  <-- return [::] bucket
  `- inet_bhash2_conflict
     `- __inet_bhash2_conflict <-- checks IPV6_ONLY for AF_INET
        |                          but not for v4-mapped-v6 address
        `- inet_bind_conflict  <-- does not check address

inet_bind_conflict() does not check socket addresses because
__inet_bhash2_conflict() is expected to do so.

However, it checks IPV6_V6ONLY attribute only against AF_INET
socket, and not for v4-mapped-v6 address.

As a result, v4-mapped-v6 address conflicts with v6-only wildcard
address.

To avoid that, let's add the missing test to use bhash2 for
v4-mapped-v6 address.

Fixes: 5e07e672412b ("tcp: Use bhash2 for v4-mapped-v6 non-wildcard address.")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240326204251.51301-2-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index c038e28e2f1e66bf10c7f67ffe073e6790b2d6ce..4184d45f890c8dc3c8012849bab29a884d1bcf2e 100644 (file)
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -203,8 +203,15 @@ static bool __inet_bhash2_conflict(const struct sock *sk, struct sock *sk2,
                                   kuid_t sk_uid, bool relax,
                                   bool reuseport_cb_ok, bool reuseport_ok)
 {
-       if (sk->sk_family == AF_INET && ipv6_only_sock(sk2))
-               return false;
+       if (ipv6_only_sock(sk2)) {
+               if (sk->sk_family == AF_INET)
+                       return false;
+
+#if IS_ENABLED(CONFIG_IPV6)
+               if (ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr))
+                       return false;
+#endif
+       }
 
        return inet_bind_conflict(sk, sk2, sk_uid, relax,
                                  reuseport_cb_ok, reuseport_ok);