lib: Fix possible crash on startup

Fix possible crash when the object creation is cancelled on startup. We
shouldn't be using user_data until we know that the call has not been
cancelled, otherwise we could be accessing already freed memory.

 #0  g_type_check_instance_cast (type_instance=type_instance@entry=0x208dc60, iface_type=34189312) at /home/hadess/Projects/jhbuild/glib/gobject/gtype.c:4057
 #1  0x00007f34c8d09522 in object_manager_new_callback (source_object=<optimized out>, res=0x208c390, user_data=user_data@entry=0x208dc60)
     at ../../../../Projects/jhbuild/gnome-bluetooth/lib/bluetooth-client.c:761
 #2  0x00007f34ce7d819a in g_task_return_now (task=0x208c390) at /home/hadess/Projects/jhbuild/glib/gio/gtask.c:1148
 #3  0x00007f34ce7d81d9 in complete_in_idle_cb (task=task@entry=0x208c390) at /home/hadess/Projects/jhbuild/glib/gio/gtask.c:1162

https://bugzilla.gnome.org/show_bug.cgi?id=793505

1 files changed, 11 insertions, 5 deletions

diff --git a/lib/bluetooth-client.c b/lib/bluetooth-client.c
index 0233537e..2a8db62f 100644
--- a/lib/bluetooth-client.c
+++ b/lib/bluetooth-client.c
@@ -758,18 +758,24 @@ object_manager_new_callback(GObject      *source_object,
 			    GAsyncResult *res,
 			    void         *user_data)
 {
-	BluetoothClient  *client = BLUETOOTH_CLIENT (user_data);
-	BluetoothClientPrivate *priv = BLUETOOTH_CLIENT_GET_PRIVATE(client);
+	BluetoothClient *client;
+	BluetoothClientPrivate *priv;
+	GDBusObjectManager *manager;
 	GList *object_list, *l;
 	GError *error = NULL;
 
-	priv->manager = g_dbus_object_manager_client_new_for_bus_finish (res, &error);
-	if (error) {
-		g_warning ("Could not create bluez object manager: %s", error->message);
+	manager = g_dbus_object_manager_client_new_for_bus_finish (res, &error);
+	if (!manager) {
+		if (!g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
+			g_warning ("Could not create bluez object manager: %s", error->message);
 		g_error_free (error);
 		return;
 	}
 
+	client = BLUETOOTH_CLIENT (user_data);
+	priv = BLUETOOTH_CLIENT_GET_PRIVATE(client);
+	priv->manager = manager;
+
 	g_signal_connect (G_OBJECT (priv->manager), "interface-added", (GCallback) interface_added, client);
 	g_signal_connect (G_OBJECT (priv->manager), "interface-removed", (GCallback) interface_removed, client);