Audit and fix GVariant reference counting

This patch series fixes a fair number of memory leaks revolving
around GVariant memory allocation and D-Bus calls. The first
patch in the series does not actually fix any leaks, only
simplifies the code; the rest are leak fixes, one or two per
patch.

9 files changed, 70 insertions, 119 deletions

diff --git a/src/polkit/polkitactiondescription.c b/src/polkit/polkitactiondescription.c
index 4bd9604..ed0655e 100644
--- a/src/polkit/polkitactiondescription.c
+++ b/src/polkit/polkitactiondescription.c
@@ -352,10 +352,10 @@ polkit_action_description_new_for_gvariant (GVariant *value)
   return action_description;
 }
 
+/* Note that this returns a floating value. */
 GVariant *
 polkit_action_description_to_gvariant (PolkitActionDescription *action_description)
 {
-  GVariant *value;
   GVariantBuilder builder;
   GHashTableIter iter;
   const gchar *a_key;
@@ -368,17 +368,15 @@ polkit_action_description_to_gvariant (PolkitActionDescription *action_descripti
     g_variant_builder_add (&builder, "{ss}", a_key, a_value);
 
   /* TODO: note 'foo ? : ""' is a gcc specific extension (it's a short-hand for 'foo ? foo : ""') */
-  value = g_variant_new ("(ssssssuuua{ss})",
-                         action_description->action_id ? : "",
-                         action_description->description ? : "",
-                         action_description->message ? : "",
-                         action_description->vendor_name ? : "",
-                         action_description->vendor_url ? : "",
-                         action_description->icon_name ? : "",
-                         action_description->implicit_any,
-                         action_description->implicit_inactive,
-                         action_description->implicit_active,
-                         &builder);
-
-  return value;
+  return g_variant_new ("(ssssssuuua{ss})",
+                        action_description->action_id ? : "",
+                        action_description->description ? : "",
+                        action_description->message ? : "",
+                        action_description->vendor_name ? : "",
+                        action_description->vendor_url ? : "",
+                        action_description->icon_name ? : "",
+                        action_description->implicit_any,
+                        action_description->implicit_inactive,
+                        action_description->implicit_active,
+                        &builder);
 }
diff --git a/src/polkit/polkitauthority.c b/src/polkit/polkitauthority.c
index 7c4db7b..71d527c 100644
--- a/src/polkit/polkitauthority.c
+++ b/src/polkit/polkitauthority.c
@@ -886,8 +886,6 @@ polkit_authority_check_authorization (PolkitAuthority               *authority,
                                       GAsyncReadyCallback            callback,
                                       gpointer                       user_data)
 {
-  GVariant *subject_value;
-  GVariant *details_value;
   CheckAuthData *data;
 
   g_return_if_fail (POLKIT_IS_AUTHORITY (authority));
@@ -896,11 +894,6 @@ polkit_authority_check_authorization (PolkitAuthority               *authority,
   g_return_if_fail (details == NULL || POLKIT_IS_DETAILS (details));
   g_return_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable));
 
-  subject_value = polkit_subject_to_gvariant (subject);
-  details_value = polkit_details_to_gvariant (details);
-  g_variant_ref_sink (subject_value);
-  g_variant_ref_sink (details_value);
-
   data = g_new0 (CheckAuthData, 1);
   data->authority = g_object_ref (authority);
   data->simple = g_simple_async_result_new (G_OBJECT (authority),
@@ -915,9 +908,9 @@ polkit_authority_check_authorization (PolkitAuthority               *authority,
   g_dbus_proxy_call (authority->proxy,
                      "CheckAuthorization",
                      g_variant_new ("(@(sa{sv})s@a{ss}us)",
-                                    subject_value,
+                                    polkit_subject_to_gvariant (subject), /* A floating value */
                                     action_id,
-                                    details_value,
+                                    polkit_details_to_gvariant (details), /* A floating value */
                                     flags,
                                     data->cancellation_id != NULL ? data->cancellation_id : ""),
                      G_DBUS_CALL_FLAGS_NONE,
@@ -925,8 +918,6 @@ polkit_authority_check_authorization (PolkitAuthority               *authority,
                      cancellable,
                      (GAsyncReadyCallback) check_authorization_cb,
                      data);
-  g_variant_unref (subject_value);
-  g_variant_unref (details_value);
 }
 
 /**
@@ -1058,20 +1049,16 @@ polkit_authority_register_authentication_agent (PolkitAuthority      *authority,
                                                 GAsyncReadyCallback   callback,
                                                 gpointer              user_data)
 {
-  GVariant *subject_value;
-
   g_return_if_fail (POLKIT_IS_AUTHORITY (authority));
   g_return_if_fail (POLKIT_IS_SUBJECT (subject));
   g_return_if_fail (locale != NULL);
   g_return_if_fail (g_variant_is_object_path (object_path));
   g_return_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable));
 
-  subject_value = polkit_subject_to_gvariant (subject);
-  g_variant_ref_sink (subject_value);
   g_dbus_proxy_call (authority->proxy,
                      "RegisterAuthenticationAgent",
                      g_variant_new ("(@(sa{sv})ss)",
-                                    subject_value,
+                                    polkit_subject_to_gvariant (subject), /* A floating value */
                                     locale,
                                     object_path),
                      G_DBUS_CALL_FLAGS_NONE,
@@ -1082,7 +1069,6 @@ polkit_authority_register_authentication_agent (PolkitAuthority      *authority,
                                                 callback,
                                                 user_data,
                                                 polkit_authority_register_authentication_agent));
-  g_variant_unref (subject_value);
 }
 
 /**
@@ -1375,19 +1361,15 @@ polkit_authority_unregister_authentication_agent (PolkitAuthority      *authorit
                                                   GAsyncReadyCallback   callback,
                                                   gpointer              user_data)
 {
-  GVariant *subject_value;
-
   g_return_if_fail (POLKIT_IS_AUTHORITY (authority));
   g_return_if_fail (POLKIT_IS_SUBJECT (subject));
   g_return_if_fail (g_variant_is_object_path (object_path));
   g_return_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable));
 
-  subject_value = polkit_subject_to_gvariant (subject);
-  g_variant_ref_sink (subject_value);
   g_dbus_proxy_call (authority->proxy,
                      "UnregisterAuthenticationAgent",
                      g_variant_new ("(@(sa{sv})s)",
-                                    subject_value,
+                                    polkit_subject_to_gvariant (subject), /* A floating value */
                                     object_path),
                      G_DBUS_CALL_FLAGS_NONE,
                      -1,
@@ -1397,7 +1379,6 @@ polkit_authority_unregister_authentication_agent (PolkitAuthority      *authorit
                                                 callback,
                                                 user_data,
                                                 polkit_authority_unregister_authentication_agent));
-  g_variant_unref (subject_value);
 }
 
 /**
@@ -1511,7 +1492,6 @@ polkit_authority_authentication_agent_response (PolkitAuthority      *authority,
                                                 GAsyncReadyCallback   callback,
                                                 gpointer              user_data)
 {
-  GVariant *identity_value;
   /* Note that in reality, this API is only accessible to root, and
    * only called from the setuid helper `polkit-agent-helper-1`.
    *
@@ -1526,14 +1506,12 @@ polkit_authority_authentication_agent_response (PolkitAuthority      *authority,
   g_return_if_fail (POLKIT_IS_IDENTITY (identity));
   g_return_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable));
 
-  identity_value = polkit_identity_to_gvariant (identity);
-  g_variant_ref_sink (identity_value);
   g_dbus_proxy_call (authority->proxy,
                      "AuthenticationAgentResponse2",
                      g_variant_new ("(us@(sa{sv}))",
                                     (guint32)uid,
                                     cookie,
-                                    identity_value),
+                                    polkit_identity_to_gvariant (identity)), /* A floating value */
                      G_DBUS_CALL_FLAGS_NONE,
                      -1,
                      cancellable,
@@ -1542,7 +1520,6 @@ polkit_authority_authentication_agent_response (PolkitAuthority      *authority,
                                                 callback,
                                                 user_data,
                                                 polkit_authority_authentication_agent_response));
-  g_variant_unref (identity_value);
 }
 
 /**
@@ -1653,18 +1630,14 @@ polkit_authority_enumerate_temporary_authorizations (PolkitAuthority     *author
                                                      GAsyncReadyCallback  callback,
                                                      gpointer             user_data)
 {
-  GVariant *subject_value;
-
   g_return_if_fail (POLKIT_IS_AUTHORITY (authority));
   g_return_if_fail (POLKIT_IS_SUBJECT (subject));
   g_return_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable));
 
-  subject_value = polkit_subject_to_gvariant (subject);
-  g_variant_ref_sink (subject_value);
   g_dbus_proxy_call (authority->proxy,
                      "EnumerateTemporaryAuthorizations",
                      g_variant_new ("(@(sa{sv}))",
-                                    subject_value),
+                                    polkit_subject_to_gvariant (subject)), /* A floating value */
                      G_DBUS_CALL_FLAGS_NONE,
                      -1,
                      cancellable,
@@ -1673,7 +1646,6 @@ polkit_authority_enumerate_temporary_authorizations (PolkitAuthority     *author
                                                 callback,
                                                 user_data,
                                                 polkit_authority_enumerate_temporary_authorizations));
-  g_variant_unref (subject_value);
 }
 
 /**
@@ -1726,11 +1698,13 @@ polkit_authority_enumerate_temporary_authorizations_finish (PolkitAuthority *aut
           g_prefix_error (error, "Error serializing return value of EnumerateTemporaryAuthorizations: ");
           g_list_foreach (ret, (GFunc) g_object_unref, NULL);
           g_list_free (ret);
-          goto out;
+          ret = NULL;
+          goto out_array;
         }
       ret = g_list_prepend (ret, auth);
     }
   ret = g_list_reverse (ret);
+ out_array:
   g_variant_unref (array);
   g_variant_unref (value);
 
@@ -1805,18 +1779,14 @@ polkit_authority_revoke_temporary_authorizations (PolkitAuthority     *authority
                                                   GAsyncReadyCallback  callback,
                                                   gpointer             user_data)
 {
-  GVariant *subject_value;
-
   g_return_if_fail (POLKIT_IS_AUTHORITY (authority));
   g_return_if_fail (POLKIT_IS_SUBJECT (subject));
   g_return_if_fail (cancellable == NULL || G_IS_CANCELLABLE (cancellable));
 
-  subject_value = polkit_subject_to_gvariant (subject);
-  g_variant_ref_sink (subject_value);
   g_dbus_proxy_call (authority->proxy,
                      "RevokeTemporaryAuthorizations",
                      g_variant_new ("(@(sa{sv}))",
-                                    subject_value),
+                                    polkit_subject_to_gvariant (subject)), /* A floating value */
                      G_DBUS_CALL_FLAGS_NONE,
                      -1,
                      cancellable,
@@ -1825,7 +1795,6 @@ polkit_authority_revoke_temporary_authorizations (PolkitAuthority     *authority
                                                 callback,
                                                 user_data,
                                                 polkit_authority_revoke_temporary_authorizations));
-  g_variant_unref (subject_value);
 }
 
 /**
diff --git a/src/polkit/polkitauthorizationresult.c b/src/polkit/polkitauthorizationresult.c
index dd3d761..877a9a6 100644
--- a/src/polkit/polkitauthorizationresult.c
+++ b/src/polkit/polkitauthorizationresult.c
@@ -290,19 +290,15 @@ polkit_authorization_result_new_for_gvariant (GVariant *value)
   return ret;
 }
 
+/* Note that this returns a floating value. */
 GVariant *
 polkit_authorization_result_to_gvariant (PolkitAuthorizationResult *authorization_result)
 {
-  GVariant *ret;
-  GVariant *details_gvariant;
-
-  details_gvariant = polkit_details_to_gvariant (polkit_authorization_result_get_details (authorization_result));
-  g_variant_ref_sink (details_gvariant);
-  ret = g_variant_new ("(bb@a{ss})",
-                       polkit_authorization_result_get_is_authorized (authorization_result),
-                       polkit_authorization_result_get_is_challenge (authorization_result),
-                       details_gvariant);
-  g_variant_unref (details_gvariant);
+  PolkitDetails *details;
 
-  return ret;
+  details = polkit_authorization_result_get_details (authorization_result);
+  return g_variant_new ("(bb@a{ss})",
+                        polkit_authorization_result_get_is_authorized (authorization_result),
+                        polkit_authorization_result_get_is_challenge (authorization_result),
+                        polkit_details_to_gvariant (details)); /* A floating value */
 }
diff --git a/src/polkit/polkitdetails.c b/src/polkit/polkitdetails.c
index 07a6f63..b16aadc 100644
--- a/src/polkit/polkitdetails.c
+++ b/src/polkit/polkitdetails.c
@@ -195,10 +195,10 @@ polkit_details_get_keys (PolkitDetails *details)
   return ret;
 }
 
+/* Note that this returns a floating value. */
 GVariant *
 polkit_details_to_gvariant (PolkitDetails *details)
 {
-  GVariant *ret;
   GVariantBuilder builder;
 
   g_variant_builder_init (&builder, G_VARIANT_TYPE ("a{ss}"));
@@ -212,8 +212,7 @@ polkit_details_to_gvariant (PolkitDetails *details)
       while (g_hash_table_iter_next (&hash_iter, (gpointer) &key, (gpointer) &value))
         g_variant_builder_add (&builder, "{ss}", key, value);
     }
-  ret = g_variant_builder_end (&builder);
-  return ret;
+  return g_variant_builder_end (&builder);
 }
 
 PolkitDetails *
diff --git a/src/polkit/polkitidentity.c b/src/polkit/polkitidentity.c
index 7813c2c..3aa1f7f 100644
--- a/src/polkit/polkitidentity.c
+++ b/src/polkit/polkitidentity.c
@@ -198,12 +198,12 @@ polkit_identity_from_string  (const gchar   *str,
   return identity;
 }
 
+/* Note that this returns a floating value. */
 GVariant *
 polkit_identity_to_gvariant (PolkitIdentity *identity)
 {
   GVariantBuilder builder;
   GVariant *dict;
-  GVariant *ret;
   const gchar *kind;
 
   kind = "";
@@ -233,8 +233,7 @@ polkit_identity_to_gvariant (PolkitIdentity *identity)
     }
 
   dict = g_variant_builder_end (&builder);
-  ret = g_variant_new ("(s@a{sv})", kind, dict);
-  return ret;
+  return g_variant_new ("(s@a{sv})", kind, dict);
 }
 
 static GVariant *
@@ -267,6 +266,7 @@ lookup_asv (GVariant            *dict,
                            g_variant_get_type_string (value),
                            type_string);
               g_free (type_string);
+              g_variant_unref (value);
               goto out;
             }
           ret = value;
diff --git a/src/polkit/polkitsubject.c b/src/polkit/polkitsubject.c
index df8e1aa..d4c1182 100644
--- a/src/polkit/polkitsubject.c
+++ b/src/polkit/polkitsubject.c
@@ -290,12 +290,12 @@ polkit_subject_from_string  (const gchar   *str,
   return subject;
 }
 
+/* Note that this returns a floating value. */
 GVariant *
 polkit_subject_to_gvariant (PolkitSubject *subject)
 {
   GVariantBuilder builder;
   GVariant *dict;
-  GVariant *ret;
   const gchar *kind;
 
   kind = "";
@@ -329,8 +329,7 @@ polkit_subject_to_gvariant (PolkitSubject *subject)
     }
 
   dict = g_variant_builder_end (&builder);
-  ret = g_variant_new ("(s@a{sv})", kind, dict);
-  return ret;
+  return g_variant_new ("(s@a{sv})", kind, dict);
 }
 
 static GVariant *
@@ -363,6 +362,7 @@ lookup_asv (GVariant            *dict,
                            g_variant_get_type_string (value),
                            type_string);
               g_free (type_string);
+              g_variant_unref (value);
               goto out;
             }
           ret = value;
diff --git a/src/polkit/polkittemporaryauthorization.c b/src/polkit/polkittemporaryauthorization.c
index b2c6003..5e07678 100644
--- a/src/polkit/polkittemporaryauthorization.c
+++ b/src/polkit/polkittemporaryauthorization.c
@@ -212,22 +212,15 @@ polkit_temporary_authorization_new_for_gvariant (GVariant  *value,
   return authorization;
 }
 
+/* Note that this returns a floating value. */
 GVariant *
 polkit_temporary_authorization_to_gvariant (PolkitTemporaryAuthorization *authorization)
 {
-  GVariant *ret;
-  GVariant *subject_gvariant;
-
-  subject_gvariant = polkit_subject_to_gvariant (authorization->subject);
-  g_variant_ref_sink (subject_gvariant);
-  ret = g_variant_new ("(ss@(sa{sv})tt)",
-                       authorization->id,
-                       authorization->action_id,
-                       subject_gvariant,
-                       authorization->time_obtained,
-                       authorization->time_expires);
-  g_variant_unref (subject_gvariant);
-
-  return ret;
+  return g_variant_new ("(ss@(sa{sv})tt)",
+                        authorization->id,
+                        authorization->action_id,
+                        polkit_subject_to_gvariant (authorization->subject), /* A floating value */
+                        authorization->time_obtained,
+                        authorization->time_expires);
 }
 
diff --git a/src/polkitbackend/polkitbackendauthority.c b/src/polkitbackend/polkitbackendauthority.c
index 64560e1..0d1fac4 100644
--- a/src/polkitbackend/polkitbackendauthority.c
+++ b/src/polkitbackend/polkitbackendauthority.c
@@ -645,11 +645,8 @@ server_handle_enumerate_actions (Server                 *server,
   for (l = actions; l != NULL; l = l->next)
     {
       PolkitActionDescription *ad = POLKIT_ACTION_DESCRIPTION (l->data);
-      GVariant *value;
-      value = polkit_action_description_to_gvariant (ad);
-      g_variant_ref_sink (value);
-      g_variant_builder_add_value (&builder, value);
-      g_variant_unref (value);
+      g_variant_builder_add_value (&builder,
+                                   polkit_action_description_to_gvariant (ad)); /* A floating value */
     }
   g_dbus_method_invocation_return_value (invocation, g_variant_new ("(a(ssssssuuua{ss}))", &builder));
 
@@ -709,11 +706,9 @@ check_auth_cb (GObject      *source_object,
     }
   else
     {
-      GVariant *value;
-      value = polkit_authorization_result_to_gvariant (result);
-      g_variant_ref_sink (value);
-      g_dbus_method_invocation_return_value (data->invocation, g_variant_new ("(@(bba{ss}))", value));
-      g_variant_unref (value);
+      g_dbus_method_invocation_return_value (data->invocation,
+                                             g_variant_new ("(@(bba{ss}))",
+                                                            polkit_authorization_result_to_gvariant (result))); /* A floating value */
       g_object_unref (result);
     }
 
@@ -956,6 +951,7 @@ server_handle_register_authentication_agent_with_options (Server
   g_dbus_method_invocation_return_value (invocation, g_variant_new ("()"));
 
  out:
+  g_variant_unref (subject_gvariant);
   if (options != NULL)
       g_variant_unref (options);
   if (subject != NULL)
@@ -1007,6 +1003,7 @@ server_handle_unregister_authentication_agent (Server                 *server,
   g_dbus_method_invocation_return_value (invocation, g_variant_new ("()"));
 
  out:
+  g_variant_unref (subject_gvariant);
   if (subject != NULL)
     g_object_unref (subject);
 }
@@ -1057,6 +1054,7 @@ server_handle_authentication_agent_response (Server                 *server,
   g_dbus_method_invocation_return_value (invocation, g_variant_new ("()"));
 
  out:
+  g_variant_unref (identity_gvariant);
   if (identity != NULL)
     g_object_unref (identity);
 }
@@ -1107,6 +1105,7 @@ server_handle_authentication_agent_response2 (Server                 *server,
   g_dbus_method_invocation_return_value (invocation, g_variant_new ("()"));
 
  out:
+  g_variant_unref (identity_gvariant);
   if (identity != NULL)
     g_object_unref (identity);
 }
@@ -1158,17 +1157,15 @@ server_handle_enumerate_temporary_authorizations (Server                 *server
   for (l = authorizations; l != NULL; l = l->next)
     {
       PolkitTemporaryAuthorization *a = POLKIT_TEMPORARY_AUTHORIZATION (l->data);
-      GVariant *value;
-      value = polkit_temporary_authorization_to_gvariant (a);
-      g_variant_ref_sink (value);
-      g_variant_builder_add_value (&builder, value);
-      g_variant_unref (value);
+      g_variant_builder_add_value (&builder,
+                                   polkit_temporary_authorization_to_gvariant (a)); /* A floating value */
     }
   g_list_foreach (authorizations, (GFunc) g_object_unref, NULL);
   g_list_free (authorizations);
   g_dbus_method_invocation_return_value (invocation, g_variant_new ("(a(ss(sa{sv})tt))", &builder));
 
  out:
+  g_variant_unref (subject_gvariant);
   if (subject != NULL)
     g_object_unref (subject);
 }
@@ -1215,6 +1212,7 @@ server_handle_revoke_temporary_authorizations (Server                 *server,
   g_dbus_method_invocation_return_value (invocation, g_variant_new ("()"));
 
  out:
+  g_variant_unref (subject_gvariant);
   if (subject != NULL)
     g_object_unref (subject);
 }
diff --git a/src/polkitbackend/polkitbackendinteractiveauthority.c b/src/polkitbackend/polkitbackendinteractiveauthority.c
index ccfd608..1cd60d3 100644
--- a/src/polkitbackend/polkitbackendinteractiveauthority.c
+++ b/src/polkitbackend/polkitbackendinteractiveauthority.c
@@ -1906,15 +1906,15 @@ authentication_agent_begin_cb (GDBusProxy   *proxy,
   AuthenticationSession *session = user_data;
   gboolean gained_authorization;
   gboolean was_dismissed;
+  GVariant *result;
   GError *error;
 
   was_dismissed = FALSE;
   gained_authorization = FALSE;
 
   error = NULL;
-  if (!g_dbus_proxy_call_finish (proxy,
-                                 res,
-                                 &error))
+  result = g_dbus_proxy_call_finish (proxy, res, &error);
+  if (result == NULL)
     {
       g_printerr ("Error performing authentication: %s (%s %d)\n",
                   error->message,
@@ -1926,6 +1926,7 @@ authentication_agent_begin_cb (GDBusProxy   *proxy,
     }
   else
     {
+      g_variant_unref (result);
       gained_authorization = session->is_authenticated;
       g_debug ("Authentication complete, is_authenticated = %d", session->is_authenticated);
     }
@@ -2299,7 +2300,6 @@ authentication_agent_initiate_challenge (AuthenticationAgent         *agent,
   gchar *localized_message;
   gchar *localized_icon_name;
   PolkitDetails *localized_details;
-  GVariant *details_gvariant;
   GList *user_identities = NULL;
   GVariantBuilder identities_builder;
   GVariant *parameters;
@@ -2397,28 +2397,21 @@ authentication_agent_initiate_challenge (AuthenticationAgent         *agent,
   add_pid (localized_details, caller, "polkit.caller-pid");
   add_pid (localized_details, subject, "polkit.subject-pid");
 
-  details_gvariant = polkit_details_to_gvariant (localized_details);
-  g_variant_ref_sink (details_gvariant);
-
   g_variant_builder_init (&identities_builder, G_VARIANT_TYPE ("a(sa{sv})"));
   for (l = user_identities; l != NULL; l = l->next)
     {
       PolkitIdentity *identity = POLKIT_IDENTITY (l->data);
-      GVariant *value;
-      value = polkit_identity_to_gvariant (identity);
-      g_variant_ref_sink (value);
-      g_variant_builder_add_value (&identities_builder, value);
-      g_variant_unref (value);
+      g_variant_builder_add_value (&identities_builder,
+                                   polkit_identity_to_gvariant (identity)); /* A floating value */
     }
 
   parameters = g_variant_new ("(sss@a{ss}sa(sa{sv}))",
                               action_id,
                               localized_message,
                               localized_icon_name,
-                              details_gvariant,
+                              polkit_details_to_gvariant (localized_details), /* A floating value */
                               session->cookie,
                               &identities_builder);
-  g_variant_unref (details_gvariant);
 
   g_dbus_proxy_call (agent->proxy,
                      "BeginAuthentication",
@@ -2444,13 +2437,18 @@ authentication_agent_cancel_cb (GDBusProxy   *proxy,
                                 GAsyncResult *res,
                                 gpointer      user_data)
 {
+  GVariant *result;
   GError *error;
+
   error = NULL;
-  if (!g_dbus_proxy_call_finish (proxy, res, &error))
+  result = g_dbus_proxy_call_finish (proxy, res, &error);
+  if (result == NULL)
     {
       g_printerr ("Error cancelling authentication: %s\n", error->message);
       g_error_free (error);
     }
+  else
+    g_variant_unref (result);
 }
 
 static void