From f067fb9bc471f176b6f6693fd9da5307c35bac3c Mon Sep 17 00:00:00 2001
From: Ray Strode <rstrode@redhat.com>
Date: Thu, 22 Jul 2021 14:46:50 -0400
Subject: [PATCH 3/3] local-display-factory: Fix overrun in session type list
 generation

Some confusion in the session type list generation from GNOME/gdm!146,
means we could actually overrun the list.

This commit fixes that.
---
 daemon/gdm-local-display-factory.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/daemon/gdm-local-display-factory.c b/daemon/gdm-local-display-factory.c
index 0bb3851f..f2da3b6e 100644
--- a/daemon/gdm-local-display-factory.c
+++ b/daemon/gdm-local-display-factory.c
@@ -202,87 +202,89 @@ get_preferred_display_server (GdmLocalDisplayFactory *factory)
 
         gdm_settings_direct_get_string (GDM_KEY_PREFERRED_DISPLAY_SERVER, &preferred_display_server);
 
         if (g_strcmp0 (preferred_display_server, "wayland") == 0) {
                 if (wayland_enabled)
                         return g_strdup (preferred_display_server);
                 else
                         return g_strdup ("xorg");
         }
 
         if (g_strcmp0 (preferred_display_server, "xorg") == 0) {
                 if (xorg_enabled)
                         return g_strdup (preferred_display_server);
                 else
                         return g_strdup ("wayland");
         }
 
         if (g_strcmp0 (preferred_display_server, "legacy-xorg") == 0) {
                 if (xorg_enabled)
                         return g_strdup (preferred_display_server);
         }
 
         return g_strdup ("none");
 }
 
 static const char *
 gdm_local_display_factory_get_session_type (GdmLocalDisplayFactory *factory,
                                             gboolean                should_fall_back)
 {
         const char *session_types[3] = { NULL };
-        gsize i, session_type_index = 0, number_of_session_types = 0;
+        gsize i, session_type_index = 0;
         g_autofree gchar *preferred_display_server = NULL;
 
         preferred_display_server = get_preferred_display_server (factory);
 
         if (g_strcmp0 (preferred_display_server, "wayland") != 0 &&
             g_strcmp0 (preferred_display_server, "xorg") != 0)
               return NULL;
 
         for (i = 0; i < G_N_ELEMENTS (session_types) - 1; i++) {
 #ifdef ENABLE_WAYLAND_SUPPORT
-            if (number_of_session_types > 0 ||
+            if (i > 0 ||
                 g_strcmp0 (preferred_display_server, "wayland") == 0) {
                     gboolean wayland_enabled = FALSE;
                     if (gdm_settings_direct_get_boolean (GDM_KEY_WAYLAND_ENABLE, &wayland_enabled)) {
-                            if (wayland_enabled && g_file_test ("/usr/bin/Xwayland", G_FILE_TEST_IS_EXECUTABLE) )
-                                    session_types[number_of_session_types++] = "wayland";
+                            if (wayland_enabled && g_file_test ("/usr/bin/Xwayland", G_FILE_TEST_IS_EXECUTABLE)) {
+                                    session_types[i] = "wayland"; continue;
+                            }
                     }
             }
 #endif
 
-            if (number_of_session_types > 0 ||
+            if (i > 0 ||
                 g_strcmp0 (preferred_display_server, "xorg") == 0) {
                     gboolean xorg_enabled = FALSE;
                     if (gdm_settings_direct_get_boolean (GDM_KEY_XORG_ENABLE, &xorg_enabled)) {
-                            if (xorg_enabled && g_file_test ("/usr/bin/Xorg", G_FILE_TEST_IS_EXECUTABLE) )
-                                    session_types[number_of_session_types++] = "x11";
+                            if (xorg_enabled && g_file_test ("/usr/bin/Xorg", G_FILE_TEST_IS_EXECUTABLE)) {
+                                    session_types[i] = "x11"; continue;
+                            }
                     }
             }
         }
 
         if (should_fall_back)
                 session_type_index++;
 
         return session_types[session_type_index];
 }
 
 static void
 on_display_disposed (GdmLocalDisplayFactory *factory,
                      GdmDisplay             *display)
 {
         g_debug ("GdmLocalDisplayFactory: Display %p disposed", display);
 }
 
 static void
 store_display (GdmLocalDisplayFactory *factory,
                GdmDisplay             *display)
 {
         GdmDisplayStore *store;
 
         store = gdm_display_factory_get_display_store (GDM_DISPLAY_FACTORY (factory));
         gdm_display_store_add (store, display);
 }
 
 /*
   Example:
   dbus-send --system --dest=org.gnome.DisplayManager \
-- 
2.32.0