net: hook socketpair() into LSM

Use the newly created LSM-hook for socketpair(). The default hook
return-value is 0, so behavior stays the same unless LSMs start using
this hook.

Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Tom Gundersen <teg@jklm.no>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: James Morris <james.morris@microsoft.com>

net/socket.c

@@ -1420,6 +1420,13 @@ int __sys_socketpair(int family, int type, int protocol, int __user *usockvec)
 		goto out;
 	}
 
+	err = security_socket_socketpair(sock1, sock2);
+	if (unlikely(err)) {
+		sock_release(sock2);
+		sock_release(sock1);
+		goto out;
+	}
+
 	err = sock1->ops->socketpair(sock1, sock2);
 	if (unlikely(err < 0)) {
 		sock_release(sock2);