[Bug 1934147] Autopkgtest regression report (systemd/245.4-4ubuntu3.12)

[Ubuntu SRU Bot]

All autopkgtests for the newly accepted systemd (245.4-4ubuntu3.12) for focal have finished running.
The following regressions have been reported in tests triggered by the package:

flatpak/1.6.5-0ubuntu0.3 (amd64)
gvfs/1.44.1-1ubuntu1 (amd64, arm64)
munin/2.0.56-1ubuntu1 (s390x)


Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].

https://people.canonical.com/~ubuntu-archive/proposed-
migration/focal/update_excuses.html#systemd

[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions

Thank you!

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https://bugs.launchpad.net/bugs/1934147

Title:
  systemd leaks abandoned session scopes

Status in snapd:
  New
Status in systemd:
  New
Status in systemd package in Ubuntu:
  Fix Committed
Status in systemd source package in Bionic:
  Fix Committed
Status in systemd source package in Focal:
  Fix Committed
Status in systemd source package in Groovy:
  Won't Fix
Status in systemd source package in Hirsute:
  Fix Committed
Status in systemd source package in Impish:
  Fix Committed

Bug description:
  [impact]

  systemd may leak sessions, leaving empty cgroups around as well as
  abandoned session scopes.

  [test case]

  on a system where the user has a ssh key that allows noninteractive
  login to localhost, and also has noninteractive sudo, run:

  $ for i in {1..100}; do sudo -b -i -u ubuntu ssh localhost -- sleep 1;
  done; for i in {1..20}; do echo 'Reloading...'; sudo systemctl daemon-
  reload; done

  check the sessions to see there have been leaked sessions:

  $ loginctl list-sessions

  SESSION  UID USER   SEAT TTY
        1 1000 ubuntu      ttyS0
      350 1000 ubuntu      
      351 1000 ubuntu      
      360 1000 ubuntu      
  ...

  to verify the sessions were leaked, clear them out with:

  $ echo '' | sudo tee
  /sys/fs/cgroup/unified/user.slice/user-1000.slice/session-*.scope/cgroup.events

  that should result in all the leaked sessions being cleaned up.

  [regression potential]

  issues during systemd pid1 reexec/reload, or issues while cleaning up
  sessions, including leaking sessions/cgroups

  [scope]

  this is needed for all releases

  upstream bug linked above, and upstream PR:
  https://github.com/systemd/systemd/pull/20199

  [original description]

  On a system that is monitored via telegraf I found many abandoned
  systemd session which I believe are created by a potential race where
  systemd is reloading unit files and at the same time a user is
  connecting to the system via ssh or is executing the su command.

  The simple reproducer

  $ for i in {1..100}; do sleep 0.2; ssh localhost sudo systemctl
  daemon-reload & ssh localhost sleep 1 & done

  Wait > 1 second

  $ jobs -p | xargs --verbose --no-run-if-empty kill -KILL

  To clean out STOPPED jobs and

  $ systemctl status --all 2> /dev/null | grep --before-context 3
  abandoned

  will produce something similar to

             │ ├─  175 su - ubuntu
             │ ├─  178 -su
             │ ├─62375 systemctl status --all
             │ └─62376 grep --color=auto --before-context 3 abandoned
  --
  ● session-273.scope - Session 273 of user ubuntu
     Loaded: loaded (/run/systemd/transient/session-273.scope; transient)
  Transient: yes
     Active: active (abandoned) since Wed 2021-06-30 13:32:03 UTC; 4min 7s ago
  --
  ● session-274.scope - Session 274 of user ubuntu
     Loaded: loaded (/run/systemd/transient/session-274.scope; transient)
  Transient: yes
     Active: active (abandoned) since Wed 2021-06-30 13:32:03 UTC; 4min 7s ago
  --
  ● session-30.scope - Session 30 of user ubuntu
     Loaded: loaded (/run/systemd/transient/session-30.scope; transient)
  Transient: yes
     Active: active (abandoned) since Wed 2021-06-30 10:05:56 UTC; 3h 30min ago
  --
  ● session-302.scope - Session 302 of user ubuntu
     Loaded: loaded (/run/systemd/transient/session-302.scope; transient)
  Transient: yes
     Active: active (abandoned) since Wed 2021-06-30 13:32:04 UTC; 4min 6s ago
  --
             │ ├─  175 su - ubuntu
             │ ├─  178 -su
             │ ├─62375 systemctl status --all
             │ └─62376 grep --color=auto --before-context 3 abandoned

  The system in question is running Bionic, systemd-237-3ubuntu10.48

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