Created attachment 160078 [details]
The lockscreen as I see it when kscreenlocker_greet crashes

SUMMARY
When I lock my screen, I see an error message telling me how to unlock my screen again using a console.
It looks like I corrupted my qmlcache that kscreenlocker_greet uses.
The file ~/.cache/kscreenlocker_greet/qmlcache/5c5649af53bb78a2255cc07dba00b5d037690788.qmlc is truncated to 12288 bytes on my system (which is exactly 12 KiB).
When I remove the file, it will be regenerated with a size of 16068 bytes and the screen lock works as expected.
I can only speculate, how this file corruption happened. In my opinion, the most likely explanation is a "full disk" that caused the file not to be written to the end. After this "incident" the file stayed corrupted until I manually deleted it.


STEPS TO REPRODUCE
1. Make sure, the screen was locked at least once before, so that the following file exists.
2. truncate -s 12288 ~/.cache/kscreenlocker_greet/qmlcache/5c5649af53bb78a2255cc07dba00b5d037690788.qmlc
3. Lock the screen.

OBSERVED RESULT
A black screen with white text that cannot be unlocked graphically. It gives me instructions, how to unlock using the console. (See attached screenshot)


EXPECTED RESULT
When a cache file was not completely written to disk before, I would expect that it is not used the next time but regenerated instead. The screen should be able to lock as normal.


SOFTWARE/OS VERSIONS
Linux-Kernel: 6.4.1
KDE Plasma Version: 5.27.6
KDE Frameworks Version: 5.107.0
Qt Version: 5.15.10

ADDITIONAL INFORMATION
The following messages appear in the journal log:
Jul 04 18:09:50 lukas kcminit[20142]: Initializing  "/usr/lib/qt/plugins/plasma/kcms/systemsettings/kcm_mouse.so"
Jul 04 18:09:50 lukas kcminit[20142]: Initializing  "/usr/lib/qt/plugins/plasma/kcms/systemsettings/kcm_touchpad.so"
Jul 04 18:09:50 lukas kcminit[20142]: kcm_touchpad: Using X11 backend
Jul 04 18:09:51 lukas kscreenlocker_greet[20147]: Qt: Session management error: networkIdsList argument is NULL
Jul 04 18:09:51 lukas kernel: QQmlThread[20165]: segfault at 7f87b2296b24 ip 00007f875fc1f781 sp 00007f873cff7580 error 4 in libQt5Qml.so.5.15.10[7f875faa7000+281000] likely on CPU 5 (core 1, socket 0)
Jul 04 18:09:51 lukas kernel: Code: c0 0f 84 62 02 00 00 4c 8d 3c 40 31 db 49 c1 e7 02 0f 1f 84 00 00 00 00 00 41 8b 45 44 48 89 ef 48 01 d8 48 83 c3 0c 4c 01 e8 <8b> 70 04 48 8d 50 08 e8 d3 c5 ff ff 4c 39 fb 75 de 66 41 83 7d 48
Jul 04 18:09:51 lukas kscreenlocker_greet[20166]: Qt: Session management error: networkIdsList argument is NULL
Jul 04 18:09:51 lukas kernel: QQmlThread[20180]: segfault at 7fe77dff8007 ip 00007fe71841f781 sp 00007fe6f4ff7580 error 4 in libQt5Qml.so.5.15.10[7fe7182a7000+281000] likely on CPU 4 (core 0, socket 0)
Jul 04 18:09:51 lukas kernel: Code: c0 0f 84 62 02 00 00 4c 8d 3c 40 31 db 49 c1 e7 02 0f 1f 84 00 00 00 00 00 41 8b 45 44 48 89 ef 48 01 d8 48 83 c3 0c 4c 01 e8 <8b> 70 04 48 8d 50 08 e8 d3 c5 ff ff 4c 39 fb 75 de 66 41 83 7d 48
Jul 04 18:09:51 lukas kscreenlocker_greet[20181]: Qt: Session management error: networkIdsList argument is NULL
Jul 04 18:09:51 lukas kernel: QQmlThread[20195]: segfault at 7f8faf415007 ip 00007f8f4e81f781 sp 00007f8f2cd6d580 error 4 in libQt5Qml.so.5.15.10[7f8f4e6a7000+281000] likely on CPU 3 (core 3, socket 0)
Jul 04 18:09:51 lukas kernel: Code: c0 0f 84 62 02 00 00 4c 8d 3c 40 31 db 49 c1 e7 02 0f 1f 84 00 00 00 00 00 41 8b 45 44 48 89 ef 48 01 d8 48 83 c3 0c 4c 01 e8 <8b> 70 04 48 8d 50 08 e8 d3 c5 ff ff 4c 39 fb 75 de 66 41 83 7d 48
Jul 04 18:09:51 lukas kscreenlocker_greet[20196]: Qt: Session management error: networkIdsList argument is NULL
Jul 04 18:09:51 lukas kernel: QQmlThread[20210]: segfault at 7f46db59cb24 ip 00007f467821f781 sp 00007f4655ff9580 error 4 in libQt5Qml.so.5.15.10[7f46780a7000+281000] likely on CPU 2 (core 2, socket 0)
Jul 04 18:09:51 lukas kernel: Code: c0 0f 84 62 02 00 00 4c 8d 3c 40 31 db 49 c1 e7 02 0f 1f 84 00 00 00 00 00 41 8b 45 44 48 89 ef 48 01 d8 48 83 c3 0c 4c 01 e8 <8b> 70 04 48 8d 50 08 e8 d3 c5 ff ff 4c 39 fb 75 de 66 41 83 7d 48