st/widget: Don't allow adding/removing "" style class

strstr() in find_class_name() will always consider "" a match so the
loop was not stopping at the end of the class_list. None of the matches
within the class_list would satisfy the return conditions, unless the
class_list was either an empty string as well or has a trailing space.
So this ends up with a match outside of the allocated string that
happens to satisfy these conditions by chance which then leads to the
class string containing some of this unrelated memory. Or it might lead
to a segfault.

This adds checks to the public API that uses find_class_name() to
prevent extensions from accidentally triggering a crash this way or
having some otherwise unexpected results.

Closes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/7152
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3006>

diff --git a/src/st/st-widget.c b/src/st/st-widget.c
index de459e3af9b059ceaace6a2e59782ddf83880ad4..6c6fd3a3fa9dd6f723c8e0e0ad087c7cb79362d5 100644 (file)
--- a/src/st/st-widget.c
+++ b/src/st/st-widget.c
@@ -1199,6 +1199,7 @@ st_widget_add_style_class_name (StWidget    *actor,
 
   g_return_if_fail (ST_IS_WIDGET (actor));
   g_return_if_fail (style_class != NULL);
+  g_return_if_fail (style_class[0] != '\0');
 
   priv = st_widget_get_instance_private (actor);
 
@@ -1225,6 +1226,7 @@ st_widget_remove_style_class_name (StWidget    *actor,
 
   g_return_if_fail (ST_IS_WIDGET (actor));
   g_return_if_fail (style_class != NULL);
+  g_return_if_fail (style_class[0] != '\0');
 
   priv = st_widget_get_instance_private (actor);
 
@@ -1269,6 +1271,8 @@ st_widget_has_style_class_name (StWidget    *actor,
   StWidgetPrivate *priv;
 
   g_return_val_if_fail (ST_IS_WIDGET (actor), FALSE);
+  g_return_val_if_fail (style_class != NULL, FALSE);
+  g_return_val_if_fail (style_class[0] != '\0', FALSE);
 
   priv = st_widget_get_instance_private (actor);
 
@@ -1313,6 +1317,8 @@ st_widget_has_style_pseudo_class (StWidget    *actor,
   StWidgetPrivate *priv;
 
   g_return_val_if_fail (ST_IS_WIDGET (actor), FALSE);
+  g_return_val_if_fail (pseudo_class != NULL, FALSE);
+  g_return_val_if_fail (pseudo_class[0] != '\0', FALSE);
 
   priv = st_widget_get_instance_private (actor);
 
@@ -1362,6 +1368,7 @@ st_widget_add_style_pseudo_class (StWidget    *actor,
 
   g_return_if_fail (ST_IS_WIDGET (actor));
   g_return_if_fail (pseudo_class != NULL);
+  g_return_if_fail (pseudo_class[0] != '\0');
 
   priv = st_widget_get_instance_private (actor);
 
@@ -1387,6 +1394,7 @@ st_widget_remove_style_pseudo_class (StWidget    *actor,
 
   g_return_if_fail (ST_IS_WIDGET (actor));
   g_return_if_fail (pseudo_class != NULL);
+  g_return_if_fail (pseudo_class[0] != '\0');
 
   priv = st_widget_get_instance_private (actor);