Public bug reported:
Title: GNOME Shell crashes (SIGABRT) on Wayland due to downstream st-cursor
fallback patch
Description:
On the current Ubuntu 26.10 development branch, GNOME Shell crashes abruptly
with signal 6 (SIGABRT), bringing down the entire Wayland session and forcing a
user logout.
Steps to reproduce:
1. Start a Wayland session on Ubuntu 26.10 (GNOME 51.0-2ubuntu1).
2. Open Google Chrome or Telegram Desktop.
3. Hover the mouse cursor over a media element (e.g., hovering over a video
player on YouTube, or media in Telegram).
4. GNOME Shell instantly crashes.
Root cause and Upstream feedback:
I originally reported this issue to the upstream GNOME developers. After
analyzing the C stack trace, they pointed out that the crash happens inside
st_cursor_constructor().
This function does not exist in upstream GNOME; it was introduced by a recent
Ubuntu downstream patch: st-cursor-Fall-back-to-Xcursor-if-a-theme-does-not-
exist.patch (commit 1fcd9bceb by Alessandro Astone).
It appears that when an application requests a specific cursor type and the
fallback logic from this patch is triggered, it ultimately causes an assertion
failure
in Clutter:
Clutter:ERROR:../clutter/clutter/clutter-cursor.c:464:clutter_cursor_type_to_name:
code should not be reached
Upstream confirmed this is an Ubuntu-only downstream bug caused by the
aforementioned patch. Please review the fallback patch logic, as it currently
breaks the
Wayland session upon standard cursor changes.
ProblemType: Bug
DistroRelease: Ubuntu 26.10
Package: gnome-shell 51.0-2ubuntu1
ProcVersionSignature: Ubuntu 7.3.0-5.5-generic 7.3.0-rc3
Uname: Linux 7.3.0-5-generic x86_64
ApportVersion: 2.36.0-0ubuntu1
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: GNOME
Date: Fri Sep 25 20:26:57 2026
DisplayManager: gdm3
SourcePackage: gnome-shell
UpgradeStatus: Upgraded to stonking on 2026-09-18 (7 days ago)
** Affects: gnome-shell (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug stonking third-party-packages wayland-session
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Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/2168585
Title:
Downstream patch st-cursor-Fall-back-to-Xcursor-if-a-theme-does-not-
exist.patch is causing SIGABRT (clutter_cursor_type_to_name) when
hovering over media elements in Wayland
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