Under certain circumstances it is possible to circumvent the security of screen locking functionality of gnome-screensaver by changing the systems physical monitor configuration.
Steps to reproduce:
1) Lock screen
2) Move mouse to removable monitor
3) hit escape key to cancel unlock dialog
4) move mouse to bring up unlock dialog on new head
5) unplug monitor
6) quickly hit keys on the keyboard
At this point gnome-screensaver will either crash, or show a black screen. If it shows a black screen then hitting "alt-f2" and then typing "pkill -f gnome-screensaver" will bring you to the session.
Created attachment 389117 [details]
handle monitor topology changes better
This addresses the issue by fixing the code paths that handle a monitor disappearing.
Note the only stable gnome release this affects is 2.28.
The code that caused this issue went into gnome-screensaver some time ago during the 2.24 devel cycle:
But we didn't get autoconfiguration of hotplugged monitors until gnome 2.28's devel cycle:
Which is a prerequisite for triggering this bug.
This has been given the name CVE-2010-0414.
Embargo is lifted and this issue is public now.
Upstream bug: https://bugzilla.gnome.org/show_bug.cgi?id=609337
Upstream commit: http://git.gnome.org/browse/gnome-screensaver/commit/?id=a5f66339be6719c2b8fc478a1d5fc6545297d950
gnome-screensaver-2.28.2-1.fc12 has been pushed to the Fedora 12 stable repository. If problems still persist, please make note of it in this bug report.
*** Bug 566774 has been marked as a duplicate of this bug. ***