libnm: avoid leaking GMainContext for sync initialization after context-busy-watcher quits

When passing a destroy notify to g_dbus_connection_signal_subscribe(),
that callback gets invoked as an idle handler of the associated
GMainContext. That caused to have yet another source attached to the
context after the NMClient gets destroyed.

Especially with synchronous initialization of NMClient that is bad,
because we may destroy the context-busy-watcher too early. That results
in removing the integration of the inner GMainContext into the caller's
context, and thus we leak the inner context indefinitely.

Avoid that leak by not passing a cleanup function to
g_dbus_connection_signal_subscribe().

Fixes: ce0e898fb476 ('libnm: refactor caching of D-Bus objects in NMClient')

1 files changed, 49 insertions, 14 deletions

diff --git a/libnm/nm-client.c b/libnm/nm-client.c
index 7e2cacc673..8c1b0b9f62 100644
--- a/libnm/nm-client.c
+++ b/libnm/nm-client.c
@@ -2996,9 +2996,12 @@ _dbus_handle_interface_removed (NMClient *self,
 }
 
 static void
-_dbus_managed_objects_changed_cb (const char *object_path,
-                                  GVariant *added_interfaces_and_properties,
-                                  const char *const*removed_interfaces,
+_dbus_managed_objects_changed_cb (GDBusConnection *connection,
+                                  const char *sender_name,
+                                  const char *arg_object_path,
+                                  const char *interface_name,
+                                  const char *signal_name,
+                                  GVariant *parameters,
                                   gpointer user_data)
 {
 	NMClient *self = user_data;
@@ -3006,19 +3009,50 @@ _dbus_managed_objects_changed_cb (const char *object_path,
 	const char *log_context;
 	gboolean changed;
 
+	nm_assert (nm_streq0 (interface_name, DBUS_INTERFACE_OBJECT_MANAGER));
+
 	if (priv->get_managed_objects_cancellable) {
 		/* we still wait for the initial GetManagedObjects(). Ignore the event. */
 		return;
 	}
 
-	if (!added_interfaces_and_properties) {
-		log_context = "interfaces-removed";
-		changed = _dbus_handle_interface_removed (self, log_context, object_path, NULL, removed_interfaces);
-	} else {
+	if (nm_streq (signal_name, "InterfacesAdded")) {
+		gs_unref_variant GVariant *interfaces_and_properties = NULL;
+		const char *object_path;
+
+		if (!g_variant_is_of_type (parameters, G_VARIANT_TYPE ("(oa{sa{sv}})")))
+			return;
+
+		g_variant_get (parameters,
+		               "(&o@a{sa{sv}})",
+		               &object_path,
+		               &interfaces_and_properties);
+
 		log_context = "interfaces-added";
-		changed = _dbus_handle_interface_added (self, log_context, object_path, added_interfaces_and_properties);
+		changed = _dbus_handle_interface_added (self, log_context, object_path, interfaces_and_properties);
+		goto out;
+	}
+
+	if (nm_streq (signal_name, "InterfacesRemoved")) {
+		gs_free const char **interfaces = NULL;
+		const char *object_path;
+
+		if (!g_variant_is_of_type (parameters, G_VARIANT_TYPE ("(oas)")))
+			return;
+
+		g_variant_get (parameters,
+		               "(&o^a&s)",
+		               &object_path,
+		               &interfaces);
+
+		log_context = "interfaces-removed";
+		changed = _dbus_handle_interface_removed (self, log_context, object_path, NULL, interfaces);
+		goto out;
 	}
 
+	return;
+
+out:
 	if (changed)
 		_dbus_handle_changes (self, log_context, TRUE);
 }
@@ -6601,12 +6635,13 @@ _init_fetch_all (NMClient *self)
 
 	priv->get_managed_objects_cancellable = g_cancellable_new ();
 
-	priv->dbsid_nm_object_manager = nm_dbus_connection_signal_subscribe_object_manager (priv->dbus_connection,
-	                                                                                    priv->name_owner,
-	                                                                                    "/org/freedesktop",
-	                                                                                    _dbus_managed_objects_changed_cb,
-	                                                                                    self,
-	                                                                                    NULL);
+	priv->dbsid_nm_object_manager = nm_dbus_connection_signal_subscribe_object_manager_plain (priv->dbus_connection,
+	                                                                                          priv->name_owner,
+	                                                                                          "/org/freedesktop",
+	                                                                                          NULL,
+	                                                                                          _dbus_managed_objects_changed_cb,
+	                                                                                          self,
+	                                                                                          NULL);
 
 	priv->dbsid_dbus_properties_properties_changed = nm_dbus_connection_signal_subscribe_properties_changed (priv->dbus_connection,
 	                                                                                                         priv->name_owner,