gnome-screensaver crashes in KVM when locking the screen

Indeed:

000:<:010e: 32: XFree86-VidModeExtension-Request(129,15): SetGamma screen=0x0000 red=9666 green=9666 blue=9666
000:<:010f: 4: Request(43): GetInputFocus
000:>:010e:Error 2=Value: major=129, minor=15, bad=257
000:>:010f:32: Reply to GetInputFocus: revert-to=Parent(0x02) focus=0x02000004

The debug log shows the fade type being set to FADE_TYPE_GAMMA_RAMP in check_gamma_extension, due to the presence of the XF86VM extension. The xtrace log shows XF86VidModeGetGammaRampSize in gamma_fade_setup return a size of zero, at which point the fade type is changed to FADE_TYPE_GAMMA_NUMBER. XF86VidModeGetGamma then successfully returns the current gamma value.

However, when trying to set the gamma in xf86_whack_gamma, XF86VidModeSetGamma causes a BadValue error on the first iteration (as shown in xtrace), even though all the values are sane. This appears to be not handled properly on KVM, and with no way of knowing this beforehand, the error should be trapped correctly

Accepted gnome-screensaver into lucid-proposed, the package will build now and be available in a few hours. Please test and give feedback here. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you in advance!

I've tested the update and confirm it's crashing before and working after upgrading

This bug was fixed in the package gnome-screensaver - 2.30.0-0ubuntu2

---------------
gnome-screensaver (2.30.0-0ubuntu2) lucid-proposed; urgency=low

  * debian/patches/15_dont_crash_on_no_fade.patch:
    - Don't crash on systems that don't support XF86VM or XRANDR gamma fade,
      by testing if fade is supported on a particular screen before
      calling the fade_setup and fade_finish virtual functions (LP: #558721)
  * debian/patches/16_dont_crash_in_kvm.patch:
    - Don't crash when the XF86VM extension doesn't allow the gamma
      to be set (LP: #581864)
  * debian/patches/14_no_fade_on_user_switch.patch:
    - Disable fade on locking to work around LP: #546578 and prevent
      the screen remaining blank after user switching. The screensaver
      will still fade-in on idle though
 -- Chris Coulson <email address hidden> Wed, 19 May 2010 11:51:40 +0100

Copied gnome-screensaver to maverick, too.