** Description changed:
+ [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
** Changed in: systemd (Ubuntu Impish)
Status: Confirmed => In Progress
** Changed in: systemd (Ubuntu Hirsute)
Status: New => In Progress
** Changed in: systemd (Ubuntu Groovy)
Status: New => In Progress
** Changed in: systemd (Ubuntu Focal)
Status: New => In Progress
--
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https://bugs.launchpad.net/bugs/1934147
Title:
systemd leaks abandoned session scopes
Status in systemd:
Unknown
Status in systemd package in Ubuntu:
In Progress
Status in systemd source package in Bionic:
New
Status in systemd source package in Focal:
In Progress
Status in systemd source package in Groovy:
In Progress
Status in systemd source package in Hirsute:
In Progress
Status in systemd source package in Impish:
In Progress
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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