https://bugs.kde.org/show_bug.cgi?id=527841
Bug ID: 527841
Summary: The SDDM Wayland greeter's own kwin_wayland instance
(not a user session — this is the login-screen
compositor, running as the sddm system user) crashes
with SIGSEGV repeatedly. Confirmed via coredumpctl: 50
occurrences over a 6-week window (2026-09-12 th
Classification: Plasma
Product: kwin
Version First 6.6.6
Reported In:
Platform: Ubuntu
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: wayland-generic
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Environment
KWin: 6.6.6-0ubuntu0.1
Qt: 6.10.2+dfsg-3
KDE Frameworks (Kirigami): 6.24.0-0ubuntu1
Mesa: 26.0.8-1ubuntu0.3
GPU: AMD Radeon Pro WX 3200 (radeonsi, polaris12)
Distro: Kubuntu 26.04 (Ubuntu 26.04 base)
Session type: Wayland
Crash command line
/usr/bin/kwin_wayland --drm --no-lockscreen --no-global-shortcuts --locale1
Backtrace (crashing thread)
#2 KCrash::defaultCrashHandler(int) ()
#5 <signal handler called>
#6 ?? () from libQt6Core.so.6
#7 QQmlComponent::progressChanged(double) () from libQt6Qml.so.6
#8 QQmlComponentPrivate::completeLoadFromModule(QAnyStringView,
QAnyStringView) () from libQt6Qml.so.6
#9 ?? () from libQt6Qml.so.6
#10 ?? () from libQt6Qml.so.6
#11 ?? () from libQt6Qml.so.6
#12 QApplicationPrivate::notify_helper(QObject*, QEvent*) ()
#13 QCoreApplication::notifyInternal2(QObject*, QEvent*) ()
#14 QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) ()
#15 QEventDispatcherUNIX::processEvents(...) ()
#16 QUnixEventDispatcherQPA::processEvents(...) ()
#17 QEventLoop::exec(...) ()
#18 QCoreApplication::exec() ()
Crashing during normal QML component loading, reached through Qt's standard
event-dispatch path. (Several internal/non-exported frames show ?? — full DWARF
debug info for these specific Qt6/Kirigami packages isn't available via
Ubuntu's debuginfod, only public symbol names, which is the ceiling we could
reach for this report.)
Timing pattern (checked directly, not assumed)
Correlated all 50 crash timestamps against real login events
(pam_unix(sddm:session): session opened) over the same window:
0 of 50 occurred within 90 seconds after a login (ruling out "crashes during
normal post-login teardown" as the explanation).
47 of 50 occurred with no login anywhere within 30 minutes before or after —
the greeter was sitting idle in the background when it crashed.
3 of 50 occurred shortly (29s–687s) before the next login, consistent with SDDM
silently auto-restarting the crashed greeter and the next login proceeding
normally.
No instance shows any sign of a login being delayed, retried, or failed because
of this crash.
So this does not appear to disrupt logins — it's a background process crashing
and quietly respawning, roughly once a day, while idle.
Reproduction
Not reliably reproducible on demand — happens spontaneously, roughly daily,
with no clear trigger identified.
--
You are receiving this mail because:
You are watching all bug changes.
