Public bug reported:
Package: mutter (libmutter-18-0 50.1-0ubuntu2.4), Ubuntu 26.04
(resolute), GNOME 50 Wayland session
Description:
gnome-shell 50.1-0ubuntu1.3 crashed with signal 11, ending the session
(forced logout).
Symbolized crash stack (debug symbols from libmutter-18-0-dbgsym
50.1-0ubuntu2.4):
#6 xkb_keymap_mod_get_index () from libxkbcommon.so.0
#7 update_state_from_modifier_state () at
src/backends/native/meta-keymap-native.c:185
#8 update_keymap_in_main () at src/backends/native/meta-keymap-native.c:236
#9-#11 glib main loop dispatch
#12 meta_context_run_main_loop ()
Cause:
update_keymap_in_main() runs on the main thread but reads
keymap_native->impl.keymap,
which belongs to the input thread. meta_keymap_native_set_keymap_in_impl()
clears and
replaces that pointer on the input thread, so the main thread can read a NULL
(or freed)
keymap and crash in xkb_keymap_mod_get_index().
How it was triggered here:
Two input sources were configured ([('ibus', 'hangul'), ('xkb', 'kr+kr104')]).
After IBus
logged "Set global engine failed: operation cancelled" several times, the
keymap was
re-applied 31 times within ~0.6 s (one Xwayland xkbcomp run each), and
gnome-shell crashed
shortly afterwards. Upstream reports the same crash when waking from the lock
screen.
Upstream status:
- Issue: https://gitlab.gnome.org/GNOME/mutter/-/work_items/4802 (closed)
- Fix: https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/5064
commit 709ef343 "backends/native: Interface with XKB only in the input thread"
merged 2026-05-13, included in mutter 50.2 and later
- It is not in 50.1-0ubuntu2.4 (updates) or 50.1-0ubuntu2.5 (proposed).
Request:
Please backport commit 709ef343 to mutter in resolute (SRU), or update to the
50.x bugfix series.
Workaround:
Configure only a single input source, so keymap switches are rare.
** Affects: mutter (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2171283
Title:
gnome-shell crashes with SIGSEGV in xkb_keymap_mod_get_index() from
update_state_from_modifier_state() — please backport upstream fix
(mutter MR !5064)
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