Possible SIGSEGV in KIdleTime

[thedoctar]

I'm using Lubuntu 22.04.1 with LXQT backports. Sometimes my lxqt-powermanagment app crashes. Stack trace can be found here: https://github.com/lxqt/lxqt-powermanagement/issues/338#issuecomment-1227275322.

Segfault happened at: 0x7fa417fc1017 <_ZN9QHashData8nextNodeEPNS_4NodeE+7>: cmpq $0x0,(%r8)
PC (0x7fa417fc1017) ok
source "$0x0" ok
destination "(%r8)" (0x5552a8253a6f) not located in a known VMA region (needed writable region)!

StacktraceTop:
QHashData::nextNode(QHashData::Node*) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
() at /lib/x86_64-linux-gnu/libKF5IdleTime.so.5
() at /lib/x86_64-linux-gnu/libQt5Core.so.5
AbstractSystemPoller::timeoutReached(int) () at /lib/x86_64-linux-gnu/libKF5IdleTime.so.5
() at /usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/org.kde.kidletime.platforms/KF5IdleTimeXcbPlugin0.so

I'm using Qt5.15 and libkf5idletime5 5.92.0-0ubuntu1.

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: libkf5idletime5 5.92.0-0ubuntu1
ProcVersionSignature: Ubuntu 5.15.0-46.49-generic 5.15.39
Uname: Linux 5.15.0-46-generic x86_64
ApportVersion: 2.20.11-0ubuntu82.1
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: LXQt
Date: Thu Aug 25 23:44:27 2022
InstallationDate: Installed on 2020-05-11 (835 days ago)
InstallationMedia: Lubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
SourcePackage: kidletime
UpgradeStatus: Upgraded to jammy on 2022-07-27 (29 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Cedders (cedric-gn)]

I get the crash every time lxqt-powermanagement dims the backlight, as described in bug 1987036. Can confirm that the fault does not occur and everything behaves as expected without any changes to `lxqt-powermanagment`(0.17.1-0ubuntu1) if the 22.04 kidletime package is replaced with the one from kinetic:

[UPGRADE] libkf5idletime5:amd64 5.92.0-0ubuntu1 -> 5.97.0-0ubuntu1

Downgrade again and the fault is there. The LXQT team at https://github.com/lxqt/lxqt/discussions/2219 suggest no code changes are needed, just LXQt recompilation and repackaging.

[thedoctar (thedoctar)]

It's possible to manually upgrade libkf5idletime5 for now; you also have to upgrade the dependencies libx11-6 and libx11-xcb1.

[Brett Keller (blkeller)]

I'm seeing this same crash in Kubuntu 22.04.1. In this case, the segfault in KIdleTime is causing Discover Notifier to crash when performing automatic updates (which relies on waiting for an idle timeout before starting). This means automatic updates essentially don't work in Kubuntu 22.04.1, since the thing that installs the updates crashes every time it runs.

See the related bug in KDE's bug tracker:
https://bugs.kde.org/show_bug.cgi?id=464223

I believe the problem was fixed in version 5.93.0, but it would be up to Ubuntu to backport the patch to Jammy's 5.92.0 version. I don't know how likely that is to happen or what, if anything, I could do to help make that happen.