gdbus: Check for NULL DBusPendingCall in g_dbus_send_message_with_reply

"Warning: if the connection is disconnected or you try to send Unix file
descriptors on a connection that does not support them, the
DBusPendingCall will be set to NULL, so be careful with this."

Check this in g_dbus_send_message_with_reply so that callers don't need
to double check for NULL if g_dbus_send_message_with_reply returned
TRUE.

This also fix crash if passing FD over D-Bus is blocked e.g. by SELinux
policy.

bluetoothd[1894]: profiles/audio/avdtp.c:session_cb()
bluetoothd[1894]: profiles/audio/avdtp.c:avdtp_parse_cmd() Received
    SET_CONFIGURATION_CMD
bluetoothd[1894]: profiles/audio/a2dp.c:endpoint_setconf_ind() Source
    0x6c5000: Set_Configuration_Ind
bluetoothd[1894]: profiles/audio/avdtp.c:avdtp_ref() 0x6df360: ref=1
bluetoothd[1894]: profiles/audio/a2dp.c:setup_ref() 0x6d32b0: ref=1
process 1894: arguments to dbus_pending_call_set_notify() were incorrect,
     assertion "pending != NULL" failed in file dbus-pending-call.c line
     636.
This is normally a bug in some application using the D-Bus library.

1 files changed, 10 insertions, 1 deletions

diff --git a/gdbus/object.c b/gdbus/object.c
index 0822fe8..268fed5 100644
--- a/gdbus/object.c
+++ b/gdbus/object.c
@@ -1510,11 +1510,20 @@ gboolean g_dbus_send_message_with_reply(DBusConnection *connection,
 					DBusMessage *message,
 					DBusPendingCall **call, int timeout)
 {
+	dbus_bool_t ret;
+
 	/* Flush pending signal to guarantee message order */
 	g_dbus_flush(connection);
 
-	return dbus_connection_send_with_reply(connection, message, call,
+	ret = dbus_connection_send_with_reply(connection, message, call,
 								timeout);
+
+	if (ret == TRUE && call != NULL && *call == NULL) {
+		error("Unable to send message (passing fd blocked?)");
+		return FALSE;
+	}
+
+	return ret;
 }
 
 gboolean g_dbus_send_error_valist(DBusConnection *connection,