Re: [PATCH v1 3/3] cgroup: relax common ancestor restriction for direct descendants

From: Tejun Heo
Date: Thu Jul 21 2016 - 11:02:47 EST

Hello, Aleksa.

On Fri, Jul 22, 2016 at 12:37:42AM +1000, Aleksa Sarai wrote:
> > Ths is of course solvable using something like libpam-cgfs or
> > libpam-cgm (and others). Since this sounds like a question of
> > policy, not mechanism, userspace seems like the right place. Is
> > there a downside to that (or, as Tejun put it, "delegating explicitly")?
> Having a PAM module requires getting an administrator to install the PAM
> module (and also presumably audit it, not to mention convincing them that
> your requirement to use containers are significant enough for them to do any
> work). It's the same problem IMO. I understand that LXC allows you to do
> this, but it requires that you get an administrator to *install* and support
> LXC (as well as the shadow-utils setuid binaries too). There are cases where
> you don't have the freedom to do that, and also "just get someone to give
> you privileges temporarily" is again punting on the problem.

The administrator has to install a new kernel to get this feature from
kernel side too. I don't think "to bypass admin" is a strong argument
for a new kernel feature especially when it's likely to cause subtle
issues as in this case.