[gnome-software: 1/2] GsApp: Fix possible thread race condition around 'launchable' property

[Philip Withnall <pwithnall src gnome org>]

commit b00a350c1d2e0c7db9001371d3c01fc151c7ac31
Author: Milan Crha <mcrha redhat com>
Date:   Mon Mar 29 10:09:26 2021 +0000

    GsApp: Fix possible thread race condition around 'launchable' property
    
    Do not overwrite already set 'launchable' property values, to avoid use-after-free
    when other thread reads the value. The property is set and valid through
    the lifetime of the object. Also avoid unnecessary static memory duplication.
    
    Closes https://gitlab.gnome.org/GNOME/gnome-software/-/issues/1128

 lib/gs-app.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)
---
diff --git a/lib/gs-app.c b/lib/gs-app.c
index 8eeaef836..e8eb9d48b 100644
--- a/lib/gs-app.c
+++ b/lib/gs-app.c
@@ -2558,7 +2558,9 @@ const gchar *
 gs_app_get_launchable (GsApp *app, AsLaunchableKind kind)
 {
        GsAppPrivate *priv = gs_app_get_instance_private (app);
+       g_autoptr(GMutexLocker) locker = NULL;
        g_return_val_if_fail (GS_IS_APP (app), NULL);
+       locker = g_mutex_locker_new (&priv->mutex);
        return g_hash_table_lookup (priv->launchables,
                                    as_launchable_kind_to_string (kind));
 }
@@ -2577,12 +2579,21 @@ void
 gs_app_set_launchable (GsApp *app, AsLaunchableKind kind, const gchar *launchable)
 {
        GsAppPrivate *priv = gs_app_get_instance_private (app);
+       gpointer current_value = NULL;
+       const gchar *key;
        g_autoptr(GMutexLocker) locker = NULL;
        g_return_if_fail (GS_IS_APP (app));
        locker = g_mutex_locker_new (&priv->mutex);
-       g_hash_table_insert (priv->launchables,
-                            g_strdup (as_launchable_kind_to_string (kind)),
-                            g_strdup (launchable));
+       key = as_launchable_kind_to_string (kind);
+       if (g_hash_table_lookup_extended (priv->launchables, key, NULL, &current_value)) {
+               if (g_strcmp0 ((const gchar *) current_value, launchable) != 0)
+                       g_debug ("Preventing app '%s' replace of %s's launchable '%s' with '%s'",
+                                priv->name, key, (const gchar *) current_value, launchable);
+       } else {
+               g_hash_table_insert (priv->launchables,
+                                    (gpointer) as_launchable_kind_to_string (kind),
+                                    g_strdup (launchable));
+       }
 }
 
 /**
@@ -5021,7 +5032,7 @@ gs_app_init (GsApp *app)
                                            g_free);
        priv->launchables = g_hash_table_new_full (g_str_hash,
                                                   g_str_equal,
-                                                  g_free,
+                                                  NULL,
                                                   g_free);
        priv->allow_cancel = TRUE;
        g_mutex_init (&priv->mutex);