Public bug reported:
What I expected to happen:
Even if a Wayland client sends invalid or unsupported window geometry, GNOME
Shell / Mutter should handle it gracefully (e.g. ignore the request or
terminate that client), without crashing the whole desktop session.
What happened instead:
While running a Wayland client that creates a regular toplevel window, GNOME
Shell crashes and the Wayland compositor restarts.
Just before the crash, the journal logs show that Mutter reports invalid
window geometry for an xdg_surface, followed by an assertion failure in
meta_window_set_stack_position_no_sync, and then GNOME Shell exits with
signal 8. Other applications then log “Lost connection to Wayland
compositor”.
Relevant journal messages:
meta_window_set_stack_position_no_sync: assertion 'window->stack_position >=
0' failed
Invalid window geometry for xdg_surface@24. Ignoring for now, but this will
result in client termination in the future.
GNOME Shell crashed with signal 8
(EE) failed to read Wayland events: Broken pipe
Lost connection to Wayland compositor.
This suggests that a client with invalid geometry is able to put Mutter
/ GNOME Shell into an inconsistent window stacking state and crash the
compositor. Regardless of whether the client behaves perfectly, the
compositor should not crash from this situation.
Steps to reproduce:
1. Log into the default Ubuntu 25.10 GNOME Wayland session
(XDG_SESSION_TYPE=wayland).
2. Run a Wayland client that creates a normal toplevel window and (apparently)
ends up with invalid window geometry under xdg-shell.
3. Observe GNOME Shell crash and restart.
4. Check the system journal and see the “Invalid window geometry for
xdg_surface” message followed by the stack position assertion and “GNOME Shell
crashed with signal 8”.
Additional information:
- The same Wayland client did not cause any GNOME Shell crashes on Ubuntu 25.04
(also using a GNOME Wayland session) on the same machine, so this appears to be
a regression in Ubuntu 25.10 / the newer GNOME Shell/Mutter stack.
- The crash is reproducible even with all GNOME Shell extensions disabled.
- The system is up to date with all Ubuntu 25.10 updates installed.
From a desktop stability perspective, it would be helpful if Mutter
handled this invalid-geometry situation without hitting the
stack_position assertion and crashing the whole session.
ProblemType: Bug
DistroRelease: Ubuntu 25.10
Package: gnome-shell 49.0-1ubuntu1
ProcVersionSignature: Ubuntu 6.17.0-6.6-generic 6.17.1
Uname: Linux 6.17.0-6-generic x86_64
ApportVersion: 2.33.1-0ubuntu3
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Sun Nov 9 08:10:22 2025
DisplayManager: gdm3
InstallationDate: Installed on 2025-02-04 (277 days ago)
InstallationMedia: Ubuntu 24.10 "Oracular Oriole" - Release amd64 (20241009.4)
ProcEnviron:
LANG=zh_CN.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
RelatedPackageVersions: mutter-common 49.0-2ubuntu5
SourcePackage: gnome-shell
UpgradeStatus: Upgraded to questing on 2025-11-08 (0 days ago)
** Affects: gnome-shell (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug questing wayland-session
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https://bugs.launchpad.net/bugs/2130963
Title:
GNOME Shell crashes when a Wayland client triggers “Invalid window
geometry for xdg_surface” and a stack position assertion failure.
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