In case it was a kernel problem (I have also had a kernel update since I last rebooted, from 4.15.0-42 to -43), I installed the latest HWE 18.04 kernel, but that did not help.
I should note that in fact the screen shield *does* sometimes activate; but when it does, pressing a key reveals only the grey background, not the login dialog. Another potential culprit might be gdm3, but of course there has been no update to that package recently. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to gnome-shell in Ubuntu. https://bugs.launchpad.net/bugs/1812373 Title: Lock screen stopped working Status in gnome-shell package in Ubuntu: New Bug description: With the update to 3.28.3-0ubuntu0.18.04.4, on two separate machines, the lock screen stopped working properly. When I enter lock, either manually (by clicking the lock screen icon) or automatically (by waiting for the lock screen timeout), the screen either freezes with the desktop still showing, or shoes the same grey background as the login screen; it does not show the normal lock screen image. Pressing a key such as space, which would normally raise the screen shield and reveal the login dialog, has no effect. Pressing Ctrl+Alt+F1 switches to the login dialog. I can then log in successfully, but all GNOME shell extensions are disabled. (A simple workaround is then to restart gnome-shell with the "r" command from the "Enter a command" dialog.) I am marking this bug as a security vulnerability because in the case that the screen simply freezes, confidential information may be displayed by the failure of the screen shield to activate. ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: gnome-shell 3.28.3-0ubuntu0.18.04.4 ProcVersionSignature: Ubuntu 4.15.0-43.46-generic 4.15.18 Uname: Linux 4.15.0-43-generic x86_64 ApportVersion: 2.20.9-0ubuntu7.5 Architecture: amd64 CurrentDesktop: GNOME Date: Fri Jan 18 10:28:59 2019 DisplayManager: gdm3 InstallationDate: Installed on 2014-11-26 (1514 days ago) InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417) SourcePackage: gnome-shell UpgradeStatus: Upgraded to bionic on 2018-08-16 (155 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1812373/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
