From 889cd056e7c7e95de67e18df9e13244d7c4c14e5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marco=20Trevisan=20=28Trevi=C3=B1o=29?= <mail@3v1n0.net>
Date: Wed, 24 May 2023 15:18:44 +0200
Subject: [PATCH] x11/x11-errors: Use the default error handler when display is
 destroyed

An X11 server connection may still be around when we close the display,
and mutter_x_error could be triggered when x11_display has been already
destroyed leading to a crash.

To prevent this use the default X11 error handler.

As per this, also move the ownership of the error traps to x11-errors.

See: https://gitlab.gnome.org/GNOME/mutter/-/issues/2835
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3020>
---
 src/x11/meta-x11-display-private.h |  2 ++
 src/x11/meta-x11-display.c         |  3 +--
 src/x11/meta-x11-errors.c          | 13 +++++++++++++
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/x11/meta-x11-display-private.h b/src/x11/meta-x11-display-private.h
index 8f9ec1e6e..6822ed4dc 100644
--- a/src/x11/meta-x11-display-private.h
+++ b/src/x11/meta-x11-display-private.h
@@ -299,4 +299,6 @@ void meta_x11_display_clear_stage_input_region (MetaX11Display *x11_display);
 
 void meta_x11_display_init_error_traps (MetaX11Display *x11_display);
 
+void meta_x11_display_destroy_error_traps (MetaX11Display *x11_display);
+
 #endif /* META_X11_DISPLAY_PRIVATE_H */
diff --git a/src/x11/meta-x11-display.c b/src/x11/meta-x11-display.c
index a965ef864..e59e02e4b 100644
--- a/src/x11/meta-x11-display.c
+++ b/src/x11/meta-x11-display.c
@@ -265,6 +265,7 @@ meta_x11_display_dispose (GObject *object)
       x11_display->xroot = None;
     }
 
+  meta_x11_display_destroy_error_traps (x11_display);
 
   if (x11_display->xdisplay)
     {
@@ -284,8 +285,6 @@ meta_x11_display_dispose (GObject *object)
   g_free (x11_display->screen_name);
   x11_display->screen_name = NULL;
 
-  g_clear_list (&x11_display->error_traps, g_free);
-
   G_OBJECT_CLASS (meta_x11_display_parent_class)->dispose (object);
 }
 
diff --git a/src/x11/meta-x11-errors.c b/src/x11/meta-x11-errors.c
index 51e705ccd..96224ed5f 100644
--- a/src/x11/meta-x11-errors.c
+++ b/src/x11/meta-x11-errors.c
@@ -205,10 +205,23 @@ delete_outdated_error_traps (MetaX11Display *x11_display)
 void
 meta_x11_display_init_error_traps (MetaX11Display *x11_display)
 {
+  g_assert (error_x11_display == NULL);
   error_x11_display = x11_display;
   XSetErrorHandler (meta_x_error);
 }
 
+void
+meta_x11_display_destroy_error_traps (MetaX11Display *x11_display)
+{
+  if (error_x11_display == NULL)
+    return;
+
+  g_assert (error_x11_display == x11_display);
+  g_clear_list (&x11_display->error_traps, g_free);
+  error_x11_display = NULL;
+  XSetErrorHandler (NULL);
+}
+
 void
 meta_x11_error_trap_push (MetaX11Display *x11_display)
 {