[Bug 1564451] Re: User processes are counted towards systemd limit for sshd processes

[Dr. Jens Rosenboom]

Do your sleep processes show up in the output of "systemctl status
ssh.service" in the CGroup section? For me they do (sample with just one
process backgrounded):

# systemctl status ssh.service
● ssh.service - OpenBSD Secure Shell server
   Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)
   Active: active (running) since Fri 2016-04-01 05:53:59 UTC; 1min 1s ago
 Main PID: 2928 (sshd)
    Tasks: 10 (limit: 512)
   CGroup: /system.slice/ssh.service
           ├─2928 /usr/sbin/sshd -D
           ├─4966 sshd: jrosenboom [priv
           ├─5087 sshd: jrosenboom at pts/
           ├─5127 -bash
           ├─5208 sudo -i
           ├─5213 sudo -i
           ├─5214 -bash
           ├─6386 sleep 100
           ├─6403 systemctl status ssh.service
           └─6404 pager

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https://bugs.launchpad.net/bugs/1564451

Title:
  User processes are counted towards systemd limit for sshd processes

Status in openssh package in Ubuntu:
  New

Bug description:
  When running Xenial, user processes are counted towards the limit for
  the ssh.service, with a limit of 512. So if I login as a normal user
  via ssh and start 512 processes, nobody will be able to login any more
  and even all other users currently logged in will not be able to start
  any new tasks. I'm not certain whether this behaviour is by design,
  but to me it looks like a critical DOS possibility, so tagging as
  security bug.

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