Lock screen disabled when attaching external screen during suspend mode

[Tobias Goerler]

Hi,

This issue bothered me for quite some time (might have even been introduced before 17.04) and seems to be present in ubuntu-mate 18.04 as well:

My default office setup is to work with an external screen attached to my Lenovo T450s. After the following steps:

(1) disconnecting the external screen

(2) closing the laptop lid, i.e. triggering suspend mode

(3) reattaching the external screen

(4) opening the laptop lid (wake up)

or

(3) opening the laptop lid (wake up) which triggers a lock screen

(4) reattaching the external screen

I automatically end up on my desktop *without any lock screen*. In addition, neither 'Ctrl+Alt+l' nor clicking on 'System/Lock Screen' would work hereafter. This functionality can, however, be restored by manually calling 'mate-screensaver-command -d && mate-screensaver-command -a'.

Just as a clarification: The external screen is crucial for this bug. Without, the wake up from suspend mode works as desired (i.e., produces a lock screen).

As this may possibly allow unauthorized people to access the laptop in unguarded moments, I would like to know whether some configuration simply became messy on my end or whether other users experience similar issues.

Thanks,
Tobias

[Etienne Papegnies (etienne-papegnies)]

Hello
Thank you for this report.
I'm unable to immediately reproduce this issue with the hardware on hand, maybe someone else will have better luck.
What you are describing sounds like a crash of mate-screensaver.
It is possible something specific about your hardware is necessary to reproduce.
Can you please provide the output of the commands:

1. xrandr # when external monitor is connected

2. inxi -G # same thing

3. apt-cache policy mate-screensaver

4. gsettings list-recursively | grep -i screensaver

Can you also please investigate your log files for any messages related to mate-screensaver crashing?

Thanks.

[Tobias Goerler (tobgo)]

Hi Etienne,

Thanks for your quick reply and the suggestions! Please find the outputs below:

$ xrandr
Screen 0: minimum 8 x 8, current 1920 x 1200, maximum 16384 x 16384
eDP-1-1 connected (normal left inverted right x axis y axis)
   1920x1080 60.02 + 60.01 59.97 59.96 59.93
   1680x1050 59.95 59.88
   1600x1024 60.17
   1400x1050 59.98
   1600x900 59.99 59.94 59.95 59.82
   1280x1024 60.02
   1440x900 59.89
   1400x900 59.96 59.88
   1280x960 60.00
   1440x810 60.00 59.97
   1368x768 59.88 59.85
   1360x768 59.80 59.96
   1280x800 59.99 59.97 59.81 59.91
   1152x864 60.00
   1280x720 60.00 59.99 59.86 59.74
   1024x768 60.04 60.00
   960x720 60.00
   928x696 60.05
   896x672 60.01
   1024x576 59.95 59.96 59.90 59.82
   960x600 59.93 60.00
   960x540 59.96 59.99 59.63 59.82
   800x600 60.00 60.32 56.25
   840x525 60.01 59.88
   864x486 59.92 59.57
   800x512 60.17
   700x525 59.98
   800x450 59.95 59.82
   640x512 60.02
   720x450 59.89
   700x450 59.96 59.88
   640x480 60.00 59.94
   720x405 59.51 58.99
   684x384 59.88 59.85
   680x384 59.80 59.96
   640x400 59.88 59.98
   576x432 60.06
   640x360 59.86 59.83 59.84 59.32
   512x384 60.00
   512x288 60.00 59.92
   480x270 59.63 59.82
   400x300 60.32 56.34
   432x243 59.92 59.57
   320x240 60.05
   360x202 59.51 59.13
   320x180 59.84 59.32
DP-1-1 disconnected (normal left inverted right x axis y axis)
HDMI-1-1 disconnected (normal left inverted right x axis y axis)
DP-1-2 connected primary 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200 59.60*+
   1920x1080 60.23
   1600x1200 60.12
   1280x1024 75.99 75.02 60.02
   1152x921 65.99
   1152x864 75.00
   1024x768 75.03 70.07 60.00
   832x624 74.55
   800x600 72.19 75.00 60.32 56.25
   640x480 75.00 72.81 66.67 59.94
   720x400 70.08
HDMI-1-2 disconnected (normal left inverted right x axis y axis)

$ inxi -G
Graphics: Card-1: Intel HD Graphics 5500
           Card-2: NVIDIA GM108M [GeForce 940M]
           Display Server: x11 (X.Org 1.19.6 ) drivers: modesetting,nvidia
           Resolution: 1920x1200@59.60hz
           OpenGL: renderer: GeForce 940M/PCIe/SSE2
           version: 4.6.0 NVIDIA 390.48

$ apt-cache policy mate-screensaver
mate-screensaver:
  Installed: 1.20.0-1
  Candidate: 1.20.0-1
  Version table:
 *** 1.20.0-1 500
        500 http://de.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
        100 /var/lib/dpkg/status

$ apt-cache policy mate-screensaver
mate-screensaver:
  Installed: 1.20.0-1
  Candidate: 1.20.0-1
  Version table:
 *** 1.20.0-1 500
        500 http://de.archive.ubuntu.com/ubuntu bionic/uni...

[Tobias Goerler (tobgo)]

Update: The problem persists after re-installing ubuntu-mate 18.04.

According to
https://ubuntu-mate.community/t/lockscreen-bypassed-by-connecting-external-monitor-on-hdmi/16707/11
it seems that other users experience the same or a similar bug:
https://bugs.launchpad.net/ubuntu-mate/+bug/1769278