Bug 498003

Summary:	Desktop shows briefly before lock scren as laptops wake up from S3/S0ix
Product:	[Plasma] plasmashell	Reporter:	Mingcong Bai <jeffbai>
Component:	Screen locking	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED DUPLICATE
Severity:	critical	CC:	cwo.kde
Priority:	NOR
Version First Reported In:	6.2.4
Target Milestone:	1.0
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	Lock screen delay

Description Mingcong Bai 2024-12-29 03:24:56 UTC

With Plasma 6 (since at least 6.2, when I upgraded), the lock screen only displays with a second-long delay (potentially longer when battery is low) when I open my laptop's lid (waking up from suspend). During this interval, KDE shows a *live* desktop as though the screen was not locked and only switches back to the lock screen after that delay. This issue is only reproducible on X11.

This seems like a pretty severe security risk? It would only take enough tries for my desktop to become vulnerable. For your reference, this issue had been found in GNOME and MATE before:

- https://bugs.launchpad.net/ubuntu/+source/unity-2d/+bug/830348
- https://github.com/mate-desktop/mate-screensaver/issues/145

Only on Plasma, the delay can be much longer before the lock screen was shown.

I have filmed this behaviour to better explain what I mean.

Comment 1 Mingcong Bai 2024-12-29 03:34:49 UTC

Created attachment 176936 [details]
Lock screen delay

Comment 2 cwo 2024-12-30 14:00:10 UTC

Thanks for the bug report! There already is an issue filed for this, marking it as a duplicate of that one.

I can confirm that it does not happen with Wayland; the lock appears immediately.

*** This bug has been marked as a duplicate of bug 485085 ***