XScreenSaver for dom0 pops up

[John Maher]

I'm getting the strangest thing on my screen. I'll be working and the XScreenSaver dialog pops up (indicating the screen is locked) and the screen goes black. However, the screen is not locked. I have to move a window around to redraw my screen. This has always happened since I started using Qubes about 3 weeks ago. There appears to be no pattern that prompts this response. Bizarre! Any thoughts?

Thanks.

John

[Gaijin]

Yeah. I had the same thing happen when I upgraded to R3.2 as well. I
asked the same thing but nobody replied.
https://groups.google.com/forum/#!topic/qubes-users/xjHi2TcYBAQ

It still happens from time to time. Seems to happen less if I have a lot
of free memory. Closing down some memory hungry AppVMs seems to lessen
it, but I haven't been able to specifically replicate it.

[John Maher]

Interesting, because I think I have more than enough memory (32 GB). Thanks.

[Gaijin]

I've got 16GB myself. It's not that the memory is full, but it seems to
happen more when I have a lot of VMs open in one desktop. That may just
be a coincidence though.

I'm glad to see it wasn't just me though. I never had this happen with
earlier versions of Qubes on the same hardware. Not sure if it might be
the XFCE or a video driver issue. (I've never installed the nVidia
drivers.)

[Andrew David Wong]

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Thank you both for reporting this. Gaijin, I'm sorry I missed your thread.

Just to confirm: Are you both using Xfce4?

Tracking the issue here:

https://github.com/QubesOS/qubes-issues/issues/2399

- --
Andrew David Wong (Axon)
Community Manager, Qubes OS
https://www.qubes-os.org
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[Gaijin]

I used the default install parameters of R3.2. xfce4-about in dom0 shows
I'm using version 4.12. The same hardware since R2 has not experienced
this.

[Andrew David Wong]

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> I used the default install parameters of R3.2. xfce4-about in dom0 shows I'm using version 4.12. The same hardware since R2 has not experienced this.
>

Understood. Thanks.

- --
Andrew David Wong (Axon)
Community Manager, Qubes OS
https://www.qubes-os.org
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[John Maher]

Sorry for the delay in responding. I used the default install for 3.2.

I also just noticed that it appears that memory is not being purged when apps are closed. Today when I "woke up" the screen from one of these odd screen saver like issues, it very briefly displayed a browser window with a site I was on yesterday. I looked carefully and confirmed that I did not actually have that window open on my system. It's as if something from yesterday's memory was sent to the screen and then closed. Rather disconcerting.

John

[Andrew David Wong]

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> Sorry for the delay in responding. I used the default install for 3.2.
>
> I also just noticed that it appears that memory is not being purged when apps are closed. Today when I "woke up" the screen from one of these odd screen saver like issues, it very briefly displayed a browser window with a site I was on yesterday. I looked carefully and confirmed that I did not actually have that window open on my system. It's as if something from yesterday's memory was sent to the screen and then closed. Rather disconcerting.
>
> John
>

I don't think that should necessarily be disconcerting. The Qubes security model does not include or rely upon purging memory at any particular time interval. It assumes that you, the authentic single user, should be the only one with access to dom0's screen content. So, the fact that you're allowed to see your screen content from yesterday doesn't constitute any violation of the security model. You're still the same trusted user as you were yesterday. (If I've misunderstood your concern, please let me know.)

- --
Andrew David Wong (Axon)
Community Manager, Qubes OS
https://www.qubes-os.org
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[Jean-Philippe Ouellet]

On Thu, Nov 3, 2016 at 12:50 AM, Andrew David Wong <a...@qubes-os.org> wrote:
> So, the fact that you're allowed to see your screen content from yesterday doesn't constitute any violation of the security model. You're still the same trusted user as you were yesterday. (If I've misunderstood your concern, please let me know.)

This is concerning from the perspective of one who expects a lock
screen to protect the confidentiality of your activities from
untrusted people who may temporarily have limited access to your
machine while it is locked.

But perhaps more seriously, if I understand the report correctly, this
also suggests to me the potential existence of some code path which
renders stale content from untrusted appvms in a full-screen
undecorated context? If that is true, and if it is reliably
triggerable from an appvm, then this would be a useful tool for one
attempting to trick a user with fake UI. This is purely theoretical,
and standard mitigations apply as normal (e.g. trusted window-manager
actions to differentiate true windows) but this still does cause some
concern.

[John Maher]

If the memory that temporarily renders to the screen is as isolated from other appvms as expected rendered content (like an open windows), then, yes, I'm not concerned about leakage from one environment to another.

I will say that it is simply disconcerting to see it display, security implications aside. More important to me, though, is the hope that this "screen saver" triggering will go away on future updates. Let me know if there is anything I can do to help that process.

John

[Opal Raava]

Hi all, I'm having the exact same issue both on my previous qubes installation and the current one. It seems to get worse when I have browser windows open, and it continues even if I disable hardware acceleration.

There is a bug tracker entry for this issue:
https://github.com/QubesOS/qubes-issues/issues/2399

The screenshot shows exactly what I'm seeing too. It's very annoying and probably not an issue with graphics drivers. If there is anything I can do to help solve it, I'd be happy to do so.

--Opal

[ianr...@gmail.com]

I found that this happened when I had the Qubes VM Manager set to appear on all desktops ("Always on Visible Worksace"). When I stopped that, it stopped the problem. Tried this 5 or 6 times on 2 different machines. Running v.3.2 with and without Feb. updates; no difference.

HTH,

--Ian

[Opal Raava]

Oh that's interesting, I found that disabling the compositor (Menu>System Tools>Window Manager Tweaks>Compositor) solves the problem for me and also for somebody else on the github tracker entry.

I can't find the 'always on visible workspaces' settings, but I also lost the tray icon for the Qubes VM Manager somehow.

[Pete Howell]

Thanks Opal! Disabling the Compositor definitely fixes this issue.