systemd/cgroups changing permissions (was: Re: Effectively criticizing decisions you disagree with in Debian)

[Ansgar Burchardt <ansgar@43-1.org>]

Hi Joel,

Joel Rees <joel.rees@gmail.com> writes:
> (6) systemd and cgroups (at minimum) end up overriding the permissions
> system. It's bad enough having SELinux and ACLs brought in to knock
> holes in the permissions system, but when arbitrary non-kernel system
> functions start getting their hands into the equation, there is no way
> to be sure that when you set any particular file under /etc or under
> ~/ -- including /etc/ssh and ~/.shh -- as mode 740, that the effective
> permissions don't end up 666 or 1147. In this case, even pid 1 is a
> group of arbitrary non-kernel functions.
>
> Permissions and race conditions are not the only ways that the
> modularity of these technologies is broken. I'm not going to try to
> enumerate them here.

I'm interested how use of systemd and cgroups will make a file in
/etc/ssh or ~/.ssh change effective permissions. Could you explain that
in simple, reproducible steps?

Ansgar