GDM blocks SIGUSR1 used in PAM scripts

Adding scripts for reproducer.

Please run:

  apport-collect 1782152

to send us more information about the system.

apport-collect 1782152 replies with "No additional information collected" message.

But this issue is reproducible with any clean bionic desktop install (since GDM needs to be the login managed).

It is NOT reproducible if I switch back to lightDM.

It does appear SIGUSR1 is special:
  https://gitlab.gnome.org/GNOME/gdm/blob/master/daemon/gdm-server.c
  https://gitlab.gnome.org/GNOME/gdm/blob/master/daemon/main.c

Next, please report the problem to the Gnome developers here:
  https://gitlab.gnome.org/GNOME/gdm/issues
and then tell us the new bug ID.

Upstream bug: https://gitlab.gnome.org/GNOME/gdm/issues/399
(not adding via "also affects projects" since LP does not parse gitlab bugtracker yet).

Updated scripts for the reproducer.

Upstream have proposed a fix:
https://gitlab.gnome.org/GNOME/gdm/merge_requests/20

Please test it when you can.

I confirm - the issue is gone after testing a build with the upstream patch applied.

Patch for Cosmic.

SRU proposal for Bionic.

SRU proposal for Xenial.

Hi Dariusz,

Before I sponsor the patch in Ubuntu, did you submitted (or at least forwarded) the patch to gdm3 debian ?

I couldn't find a debian bug about it.

If one exist great, but if none, could you please file one against gdm3 (debian).
This will prevent gdm Ubuntu package to re-introduce the same problem in later future release sync (Debian->Ubuntu).

Once done, I'll gladly sponsor in Cosmic.

- Eric

Is that really necessary when the fix is already upstream?

Although I originally shared Daniel's doubt, I reported it to Debian and shared the patch (bug linked above).

This bug was fixed in the package gdm3 - 3.28.2-3ubuntu4

---------------
gdm3 (3.28.2-3ubuntu4) cosmic; urgency=medium

  * ubuntu_nvidia_prime.patch:
    - Run scripts for Prime before and after Gdm sessions (LP: #1778011).

 -- Alberto Milone <email address hidden> Mon, 30 Jul 2018 18:31:17 +0200

Did Alberto release the fix there and just forget to document it?

Yes. The fix for this bug is in 3.28.2-3ubuntu4

Dariusz, do we want that one in Xenial as well? If so do you plan to work on that? (assigning to you, feel free to unassign/comment/change as appropriate)

Seb, Xenial is also affected (as long as the user switches to gdm) and this patch fixes it, so it's worth having it.

I already talked to Eric (slashd) about it - he's going to drive it forward.

Hello Dariusz, or anyone else affected,

Accepted gdm3 into bionic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/gdm3/3.28.3-0ubuntu18.04.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on 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-bionic to verification-done-bionic. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-bionic. In either case, without details of your testing we will not be able to proceed.

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

Hello Dariusz, or anyone else affected,

Accepted gdm3 into xenial-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/gdm3/3.18.3-0ubuntu2.2 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on 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-xenial to verification-done-xenial. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-xenial. In either case, without details of your testing we will not be able to proceed.

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

Verified on bionic with 3.28.3-0ubuntu18.04.1.

Verified on xenial with 3.18.3-0ubuntu2.2.

This bug was fixed in the package gdm3 - 3.18.3-0ubuntu2.2

---------------
gdm3 (3.18.3-0ubuntu2.2) xenial; urgency=medium

  * d/p/unblock-sigusr1.patch:
    - Unblock SIGUSR1 before PAM. (LP: #1782152)

 -- Dariusz Gadomski <email address hidden> Mon, 23 Jul 2018 14:34:31 +0200

The verification of the Stable Release Update for gdm3 has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

This bug was fixed in the package gdm3 - 3.28.3-0ubuntu18.04.1

---------------
gdm3 (3.28.3-0ubuntu18.04.1) bionic; urgency=medium

  [ Iain Lane ]
  * New upstream release 3.28.3 (LP: #1786933):
    - CVE-2018-14424 - double free fix
      + 0001-display-store-Pass-the-display-object-rather-than-th.patch: Drop.
    - lifecycle fixes to libgdm/GdmClient
    - follow up fixes dealing with login screen reaping form last release
    - allow pam modules to use SIGUSR1 (LP: #1782152)
    - set PWD for user session
    - tell cirrus not to use wayland
  * Drop backported patches included in this release:
    - libgdm-drop-support-for-serializing-multiple-opens.patch
    - libgdm-fix-pointer-boolean-task-confusion.patch
    - libgdm-don-t-keep-manager-proxy-around-longer-than-we-nee.patch
    - libgdm-use-g_object_unref-instead-of-g_clear_object-for-w.patch
    - libgdm-get-connection-explicitly.patch
    - libgdm-Drop-weak-refs-on-the-GDBusConnection.patch
    - libgdm-Unref-the-manager-propagated-from-task.patch
    - libgdm-Don-t-double-ref-the-connection-got-from-task.patch
    - libgdm-Don-t-leak-connection-on-sync-re-authentication.patch
    - libgdm-Use-auto-pointers-and-cleanup-code.patch
    - libgdb-Try-to-reuse-connections-from-the-available-proxie.patch
    - libgdm-Don-t-save-manager-address.patch
    - libgdm-Return-NULL-on-invalid-client-instances.patch
    - daemon-gdm-session-record.c-open-close-the-utmp-database.patch

  [ Alberto Milone ]
  * ubuntu_nvidia_prime.patch:
    - Run scripts for Prime before and after Gdm sessions (LP: #1778011).

 -- Iain Lane <email address hidden> Fri, 17 Aug 2018 16:53:31 +0100