linux-kernel - Re: [PATCHv2 7/7] cgroup: mount cgroupns-root when inside non-init cgroupns

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Message-ID: <CAGr1F2Es3nkWePqRpKoAFoRB5SZp=BvQh7espyxjaRy_fYAbCw@mail.gmail.com>
Date:	Thu, 6 Nov 2014 09:28:25 -0800
From:	Aditya Kali <adityakali@...gle.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Li Zefan <lizefan@...wei.com>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	cgroups@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Linux Containers <containers@...ts.linux-foundation.org>,
	Rohit Jnagal <jnagal@...gle.com>
Subject: Re: [PATCHv2 7/7] cgroup: mount cgroupns-root when inside non-init cgroupns

On Tue, Nov 4, 2014 at 5:57 AM, Tejun Heo <tj@...nel.org> wrote:
> Hello, Aditya.
>
> On Mon, Nov 03, 2014 at 03:12:28PM -0800, Aditya Kali wrote:
>> I think the sane-behavior flag is only temporary and will be removed
>> anyways, right? So I didn't bother asking user to supply it. But I can
>> make the change as you suggested. We just have to make sure that tasks
>> inside cgroupns cannot mount non-default hierarchies as it would be a
>> regression.
>
> I'm not sure whether supporting mounting from inside a ns is even
> necessary but, if it is, can't you just test against cgrp_dfl_root?
> There's no reason to do anything differnetly for ns mounting.
>

I am not sure I fully understand what you mean. But we don't have a
way to test against cgrp_dfl_root while parsing mount-options. They
only way we know that user is trying to mount a default hierarchy is
via the sane_behavior flag. So I need to test against this flag it if
we want to restrict processes inside cgroupns to mounting the default
hierarchy only.
Or are you suggesting that its OK for nsown_capable(CAP_SYS_ADMIN)
processes to mount any cgroup hierarchy (irrespective of their
cgroupns)? I assumed that this will be a undesirable.

> Thanks.
>
> --
> tejun


Thanks,
-- 
Aditya
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