[SRU] slick-greeter crashes after recent systemd update

Bug #1902879 reported by Alkis Georgopoulos on 2020-11-04
This bug affects 2 people
Affects Status Importance Assigned to Milestone
slick-greeter (Ubuntu)

Bug Description

Systemd 237-3ubuntu10.43 landed this week in Bionic, and it enforces memory limits (LP: #1830746).

This makes slick-greeter crash, which people observe as "black screen with blinking cursor".

seb128 proposed that we need this commit backported:

Similar issues have also been discussed in LP: #1662244 and in https://github.com/canonical/lightdm/issues/55.

[Test case]
Try to boot with an up to date Ubuntu MATE 18.04 system, without having autologin enabled. A black screen with a blinking cursor will appear, instead of lightdm/slick-greeter.

[Regression potential]
The call was there to help protecting the password from being kept in memory an attacker could potential read. It's not an API which is right to use in that context though (the patch comments have details) and is simply not working as intended. In theory it could slightly weaken the code but that's better than having it no working. The same tradeoff was already made upstream in newer versions and in the different distros, unity-greeter already had the change in bionic.

Sebastien Bacher (seb128) wrote :

There was a similar issue in lightdm-gtk-greeter that got fixed in 20.10, we would need to check if the systemd SRU also triggers the bug on xubuntu in older stable series

Alkis Georgopoulos (alkisg) wrote :

I verify that the patch that seb128 proposed solves the issue for slick-greeter.
Should I link a branch with it applied, will it speed up the resolution of this issue?

Alkis Georgopoulos (alkisg) wrote :

I couldn't find the slick-greeter git sources in launchpad so I uploaded a patched version in https://code.launchpad.net/~ts.sch.gr/+git/slick-greeter.
I also used a recipe to build it, the updated packages are available in the Greek schools PPA if anyone needs them:

Sebastien Bacher (seb128) wrote :

SRU uploaded to bionic, does anyone know if the same fix is needed for focal?

Could you also add the SRU informations to the description? (impact, test case, regression potential)

Changed in slick-greeter (Ubuntu):
importance: Undecided → High
status: New → In Progress
status: In Progress → Fix Released
Alkis Georgopoulos (alkisg) wrote :

Thank you Sebastien,

I updated the title and description with the SRU information.
Focal isn't impacted by this, no need to SRU there, it's only needed for bionic.

description: updated
summary: - slick-greeter crashes after recent systemd update
+ [SRU] slick-greeter crashes after recent systemd update
Sebastien Bacher (seb128) wrote :

Thanks, checking indeed the fix is in 1.2.6 and focal has 1.3.2

description: updated

Hello Alkis, or anyone else affected,

Accepted slick-greeter into bionic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/slick-greeter/1.1.4-1ubuntu0.18.04.1 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, what testing has been performed on the package 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 for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

Changed in slick-greeter (Ubuntu Bionic):
status: New → Fix Committed
tags: added: verification-needed verification-needed-bionic
Alkis Georgopoulos (alkisg) wrote :

Thank you Andy,

slick-greeter 1.1.4-1ubuntu0.18.04.1 from proposed did indeed solve the problem for me in Ubuntu MATE 18.04. I'll set the appropriate verification tag.

tags: added: verification-done-bionic
removed: verification-needed-bionic
Christian S. (christian-stein2) wrote :

slick-greeter 1.1.4-1ubuntu0.18.04.1 solves the problem for me in Lubuntu 18.04

Launchpad Janitor (janitor) wrote :

This bug was fixed in the package slick-greeter - 1.1.4-1ubuntu0.18.04.1

slick-greeter (1.1.4-1ubuntu0.18.04.1) bionic; urgency=medium

  * debian/patches/git-new-systemd.patch:
    - remove a memory protection call which is leading to the greeter to
      error out with the new systemd (lp: #1902879)

 -- Sebastien Bacher <email address hidden> Thu, 05 Nov 2020 11:07:31 +0100

Changed in slick-greeter (Ubuntu Bionic):
status: Fix Committed → Fix Released

The verification of the Stable Release Update for slick-greeter has completed successfully and the package is now being 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.

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