[Bug 1934147] Re: systemd leaks abandoned session scopes

[Nicolas Bock]

** Description changed:

  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 ssh localhost sudo systemctl daemon-reload & ssh localhost sleep 1 & done
- jobs -p | xargs --verbose --no-run-if-empty kill -KILL
- systemctl status --all 2> /dev/null | grep --before-context 3 abandoned
+ $ for i in {1..100}; do sleep 0.2; ssh localhost sudo systemctl daemon-
+ reload & ssh localhost sleep 1 & done
+ 
+ $ 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
+            │ ├─  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)
+    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
+    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)
+    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
+    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)
+    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
+    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)
+    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
+    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
+            │ ├─  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

** Description changed:

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

Title:
  systemd leaks abandoned session scopes

Status in systemd package in Ubuntu:
  New

Bug 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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