Public bug reported:
GNOME Shell crashes with SIGSEGV during monitor hotplug while a monitor
screen-cast stream is active. The resolved core shows
is_cursor_in_stream() calling meta_logical_monitor_get_layout() with
logical_monitor=NULL while handling a cursor update triggered by a
monitor configuration rebuild.
Incident: October 27, 2026, 20:25:40 America/Los_Angeles.
Machine: rk-evo-x2.
Ubuntu 26.04.1 LTS (Resolute Raccoon), Wayland session.
GNOME Shell: 50.1-0ubuntu1.4
libmutter-18-0: 50.1-0ubuntu2.4
Kernel: 7.3.0-strix-test, custom build, #1 SMP PREEMPT_DYNAMIC Mon Oct 26
20:14:03 PDT 2026 x86_64.
Trigger and reproduction:
The core confirms a KMS connection-change timeout followed by
handle_hotplug_event(). A monitor screen-cast stream is active and attempts to
update cursor metadata during the resulting monitor configuration rebuild. The
exact physical cable sequence for this particular incident has not been
independently recorded. No deliberate reproduction was performed because the
crash terminates the desktop session.
Expected: Monitor changes are handled without crashing the compositor. A stream
whose monitor is temporarily unavailable should tolerate that transition.
Actual: Null logical monitor is dereferenced and GNOME Shell terminates with
SIGSEGV.
Relevant resolved frames (intermediate signal and GLib dispatch frames omitted):
#6 meta_logical_monitor_get_layout(logical_monitor=0x0)
../src/backends/meta-logical-monitor.c:196
#7 is_cursor_in_stream(monitor_src=0x7e8074097f20)
../src/backends/meta-screen-cast-monitor-stream-src.c:266
#8 should_cursor_metadata_be_set()
../src/backends/meta-screen-cast-monitor-stream-src.c:931
#9 meta_screen_cast_monitor_stream_src_set_cursor_metadata()
../src/backends/meta-screen-cast-monitor-stream-src.c:997
#13 meta_screen_cast_stream_src_record_frame_with_timestamp()
flags=META_SCREEN_CAST_RECORD_FLAG_CURSOR_ONLY
../src/backends/meta-screen-cast-stream-src.c:1289
#25 clutter_cursor_emit_texture_changed()
#36 meta_backend_monitors_changed()
#38 meta_monitor_manager_rebuild(config=0x0)
#40 meta_monitor_manager_native_apply_monitors_config()
#41 meta_monitor_manager_apply_monitors_config(config=0x0,
method=META_MONITORS_CONFIG_METHOD_TEMPORARY)
#42 meta_monitor_manager_ensure_configured()
#43 handle_hotplug_event()
../src/backends/native/meta-monitor-manager-native.c:339
#44 on_kms_resources_changed()
#50 meta_kms_emit_resources_changed(changes=META_KMS_RESOURCE_CHANGE_FULL)
#51 connection_change_timeout()
../src/backends/native/meta-kms-connector.c:1166
Attachment: rk-evo-x2-gnome-shell-backtrace-symbols-20261027.txt
This contains all 42 thread backtraces, generated from the saved Apport core
with GDB and matching symbols downloaded from debuginfod.ubuntu.com. Some
unrelated library frames remain unresolved.
Potentially related, but a different crash signature:
https://bugs.launchpad.net/bugs/2149858
That report concerns SIGABRT in meta_kms_update_mode_set() with a device/CRTC
assertion. The present report is SIGSEGV in monitor screen-cast cursor
handling. No common root cause has been established.
** Affects: mutter (Ubuntu)
Importance: Undecided
Status: New
** Attachment added: "GDB backtraces for all 42 threads with matching Ubuntu
debug symbols"
https://bugs.launchpad.net/bugs/2172435/+attachment/6013265/+files/rk-evo-x2-gnome-shell-backtrace-symbols-20261027.txt
--
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/2172435
Title:
Mutter crashes in is_cursor_in_stream during monitor hotplug while
screen sharing
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/2172435/+subscriptions
--
ubuntu-bugs mailing list
[email protected]
https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
