Re: Re: XScreenSaver 5.45: Disconnecting a video output can cause XScreenSaver to crash and unlock

["Mike O'Connor" <mjo () dojo mi org>]

:On Sat, Jun 05, 2021 at 02:55:10AM +0200, Marek Marczykowski-Górecki wrote:
:> The issue affects only XScreenSaver version 5.45. Versions 5.44 and
:> older, as well as 6.00, are not affected. The XScreenSaver author was
:> notified about this issue and decided not to publish an advisory, as the
:> issue does not affect the most recent version.
:> 
:> The Qubes Security Team has decided to address this issue in Qubes OS by
:> patching this specific bug rather than immediately upgrading to the 6.00
:> version.
:
:And here is the patch applied in Qubes OS:
:https://github.com/QubesOS/qubes-xscreensaver/blob/master/0001-Fix-updating-outputs-info.patch

Having said that, one of the big changes in XScreenSaver 6.00 involves
security improvements for this situation, so it's worth noting here:

https://www.jwz.org/blog/2021/04/xscreensaver-6-00-out-now/

        I have significantly refactored the XScreenSaver daemon, the
        component of the XScreenSaver suite that provides screen
        locking on X11 systems.

        These changes greatly reduce the amount of code running in the
        "critical" section: the part of the code where a crash would
        cause the screen to unlock. That critical section is now only
        around 1,800 lines of code, a reduction of roughly 87%.

etc.


-- 
 Michael J. O'Connor                                          mjo () dojo mi org
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"I never look back, darling.  It distracts me from the now."       -Edna Mode