[libvirt] [libvirt-glib] Check arguments to public GVirConfigObject methods

[Christophe Fergeau]

GVirConfigObject public methods don't have g_return_if_fail checks
on their arguments. It happens that GNOME Boxes tries to call
gvir_config_object_to_xml with a NULL GVirConfigObject causing a
crash https://bugzilla.gnome.org/show_bug.cgi?id=676308
While GNOME Boxes needs to be fixed not to pass an invalid value
to gvir_config_object_to_xml, it's better if libvirt-gconfig sanity
checks the argument it is passed by the caller before using them.
---
 libvirt-gconfig/libvirt-gconfig-object.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/libvirt-gconfig/libvirt-gconfig-object.c b/libvirt-gconfig/libvirt-gconfig-object.c
index 8286bcb..1474393 100644
--- a/libvirt-gconfig/libvirt-gconfig-object.c
+++ b/libvirt-gconfig/libvirt-gconfig-object.c
@@ -191,11 +191,16 @@ static void gvir_config_object_init(GVirConfigObject *conn)
 void gvir_config_object_validate(GVirConfigObject *config,
                                  GError **err)
 {
-    GVirConfigObjectPrivate *priv = config->priv;
+    GVirConfigObjectPrivate *priv;
     xmlRelaxNGParserCtxtPtr rngParser = NULL;
     xmlRelaxNGPtr rng = NULL;
     xmlRelaxNGValidCtxtPtr rngValid = NULL;
 
+    g_return_if_fail(GVIR_CONFIG_IS_OBJECT(config));
+    g_return_if_fail(err == NULL || *err == NULL);
+
+    priv = config->priv;
+
     xmlSetGenericErrorFunc(NULL, gvir_xml_generic_error_nop);
     xmlSetStructuredErrorFunc(NULL, gvir_xml_structured_error_nop);
 
@@ -256,13 +261,16 @@ void gvir_config_object_validate(GVirConfigObject *config,
 
 gchar *gvir_config_object_to_xml(GVirConfigObject *config)
 {
+    g_return_val_if_fail(GVIR_CONFIG_IS_OBJECT(config), NULL);
+
     return gvir_config_xml_node_to_string(config->priv->node);
 }
 
 const gchar *gvir_config_object_get_schema(GVirConfigObject *config)
 {
-    GVirConfigObjectPrivate *priv = config->priv;
-    return priv->schema;
+    g_return_val_if_fail(GVIR_CONFIG_IS_OBJECT(config), NULL);
+
+    return config->priv->schema;
 }
 
 /* FIXME: will we always have one xmlNode per GConfig object? */
-- 
1.7.10.1