Crashes running display server scripts for non X servers

[Tony Themelis]

[Impact]
Running non X server setups (e.g. Unity 8) and having display server scripts configured leads to LightDM crashing. This is due to a faulty assumption in LightDM assuming all display servers are X servers. Commonly caused by having nVidia prime support installed. Error reports in [1].

[Test Case]
1. Install the Unity 8 desktop preview
2. Configure a display setup script in the LightDM configuration:
 [SeatDefaults]
 display-setup-script=...
3. Start LightDM
4. Log in Unity 8
Expected result:
Setup script is run and you are logged into Unity 8
Observed result:
LightDM crashes

[Regression Potential]
Low, fix is simple. Tested with regression tests.

[1] https://errors.ubuntu.com/bucket/?id=/usr/sbin/lightdm%3A11%3Ax_server_local_get_authority_file_path%3Aseat_xlocal_run_script%3Arun_script%3Adisplay_server_ready_cb%3A_g_closure_invoke_va

[Apport retracing service (apport)]

StacktraceTop:
 x_server_local_get_authority_file_path (server=server@entry=0x7f4a4000a960) at x-server-local.c:304
 seat_xlocal_run_script (seat=0x22559e0, display_server=0x7f4a4000a960, script=0x224e070) at seat-xlocal.c:290
 run_script (seat=seat@entry=0x22559e0, display_server=display_server@entry=0x7f4a4000a960, script_name=0x2260a10 "/sbin/prime-offload", user=user@entry=0x0) at seat.c:302
 display_server_ready_cb (display_server=0x7f4a4000a960, seat=0x22559e0) at seat.c:1197
 _g_closure_invoke_va (closure=0x2281970, return_value=0x0, instance=0x7f4a4000a960, args=0x7fffc7c0b568, n_params=0, param_types=0x0) at /build/buildd/glib2.0-2.40.0/./gobject/gclosure.c:831

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Robert Ancell (robert-ancell)]

Is this still occurring for anyone? Does it only happen when you switch from Unity 8 to Unity 7?

[Robert Ancell (robert-ancell)]

Found it - this is when you have script hooks for the display server [1] LightDM makes an incorrect assumption that you are running X.

[1] from /usr/share/lightdm/lightdm.conf.d/90-nvidia.conf in this case.

[Launchpad Janitor (janitor)]

This bug was fixed in the package lightdm - 1.12.0-0ubuntu2

---------------
lightdm (1.12.0-0ubuntu2) utopic; urgency=medium

  * Restore 1.11.9-0ubuntu2, it was reverted by error in the previous upload
 -- Sebastien Bacher <email address hidden> Tue, 30 Sep 2014 11:25:09 +0200

[Brian Murray (brian-murray)]

Thanks for uploading the fix for this bug report to -proposed. However, when reviewing the package in -proposed and the details of this bug report I noticed that the bug description is missing information required for the SRU process. You can find full details at http://wiki.ubuntu.com/StableReleaseUpdates#Procedure but essentially this bug is missing some of the following: a statement of impact, a test case and details regarding the regression potential. Thanks in advance!

[Mathew Hodson (mhodson)]

https://launchpad.net/ubuntu/+source/lightdm/1.10.3-0ubuntu2 is available in trusty-proposed.

---------------
lightdm (1.10.3-0ubuntu2) trusty; urgency=medium

  * Refresh patches

 -- Robert Ancell <email address hidden> Fri, 10 Oct 2014 21:24:51 +1300

lightdm (1.10.3-0ubuntu1) trusty; urgency=medium

  * New upstream release:
    - Fix crash when having configuration keys defined in multiple places
      (LP: #1377373)
    - Allow user switching in multi-seat until bug stopping greeter showing on
      logout is fixed
    - Don't access .dmrc files until information from these files is required
      (LP: #1370852)
    - Do timed autologin each time you are returned to the greeter
      (LP: #1302491)

 -- Robert Ancell <email address hidden> Thu, 09 Oct 2014 09:01:21 +1300

lightdm (1.10.2-0ubuntu1) trusty; urgency=medium

  * New upstream release:
    - Use logind to provide the list of seats to use. This is disabled unless
      logind-load-seats (in [LightDM] section) is set to true. This is the
      default behaviour in lightdm 1.12. (LP: #1190581)
    - Fix crash if running script hooks with non-X display servers.
      (LP: #1305006)
    - Add a seat option 'allow-user-switching' that can disable all user
      switching for that seat. (LP: #1350357)
    - Make PAM services configurable. (LP: #1348251)
    - Add liblightdm method to get user UID. (LP: #1370327)
    - Add a new session type 'mir-container' that allows the session to run
      inside a custom system compositor. (LP: #1359332)
    - Add --show-config option that shows combined configuration.
    - Use XDG_SESSION_ID from PAM instead of using the logind D-Bus API.
      (LP: #1364725)
    - Make socket writing code used between greeter and daemon more robust to
      errors.
    - Correct section name in default users.conf file.
    - Fix tests failing with Qt 5.3 due to it checking getuid/geteuid which we
      are faking.
    - Fix small memory leaks.
    - Test improvements

 -- Robert Ancell <email address hidden> Wed, 17 Sep 2014 16:27:53 +1200

[Mathew Hodson (mhodson)]

lightdm is available in the trusty-proposed repository and at https://launchpad.net/ubuntu/+source/lightdm/1.10.3-0ubuntu2 .

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

[Robert Ancell (robert-ancell)]

Confirmed fixed in 1.10.3-0ubuntu2

[Launchpad Janitor (janitor)]

This bug was fixed in the package lightdm - 1.10.3-0ubuntu2

---------------
lightdm (1.10.3-0ubuntu2) trusty; urgency=medium

  * Refresh patches
 -- Robert Ancell <email address hidden> Fri, 10 Oct 2014 21:24:51 +1300