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

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Date:	Fri, 22 Jul 2016 01:07:13 +1000
From:	Aleksa Sarai <asarai@...e.de>
To:	Tejun Heo <tj@...nel.org>,
	James Bottomley <James.Bottomley@...senPartnership.com>
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
Subject: Re: [PATCH v1 3/3] cgroup: relax common ancestor restriction for
 direct descendants

>> I have heard
>>
>>  * it would give power to move other tasks to more rigid constraints.
>>     To which the answer is only to allow movememnt of tasks in the
>>    current cgroupns
>>  * It violates the permissions delegation model.  This one doesn't
>>    really make too much sense to me: in the same way the userns is root
>>    in its own domain, cgroups ns is effective root for the restricted
>>    cgroups (and only for processes within its ns).
>>
>> Perhaps the question should be asked the other way around:  if we were
>> explicitly delegating permission to every user in the system to set up
>> their own sub cgroups, how would you advise it be done?
>
> Coordinate in userspace.  Request whatever is managing the cgroup
> hierarchy to set up delegation.  It's not like permission model is
> fully contained in kernel on modern systems anyway.

My experience with certain systemdaemons' cgroup handling doesn't 
inspire confidence :/ (from the runC side, we've had nothing but 
issues). Also, how do you even boot into a cgroupv2 system with systemd 
(I started backporting patches to openSUSE, but it's still not booting)?

-- 
Aleksa Sarai
Software Engineer (Containers)
SUSE Linux GmbH
https://www.cyphar.com/