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

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Date:	Thu, 21 Jul 2016 11:01:35 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Aleksa Sarai <asarai@...e.de>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Li Zefan <lizefan@...wei.com>,
	Johannes Weiner <hannes@...xchg.org>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	Aditya Kali <adityakali@...gle.com>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	Christian Brauner <cbrauner@...e.de>, dev@...ncontainers.org,
	James Bottomley <James.Bottomley@...senpartnership.com>
Subject: Re: [PATCH v1 3/3] cgroup: relax common ancestor restriction for
 direct descendants

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.

Thanks.

-- 
tejun