linux-kernel - Re: [PATCH v3 2/2] cgroup: allow management of subtrees by new cgroup namespaces

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Message-ID: <20160502160604.GR7822@mtj.duckdns.org>
Date:	Mon, 2 May 2016 12:06:04 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Aleksa Sarai <asarai@...e.de>
Cc:	Li Zefan <lizefan@...wei.com>,
	Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, dev@...ncontainers.org,
	Aleksa Sarai <cyphar@...har.com>
Subject: Re: [PATCH v3 2/2] cgroup: allow management of subtrees by new
 cgroup namespaces

Hello,

On Tue, May 03, 2016 at 12:01:21AM +1000, Aleksa Sarai wrote:
> Allow an unprivileged processes to control subtrees of their associated
> cgroup, a necessary feature if an unprivileged container (set up with an
> unprivileged user namespace) wishes to take advantage of cgroups for its
> own subprocesses.
> 
> Change the mode of the cgroup directory for each cgroup association,
> allowing the process to create subtrees and modify the limits of the
> subtrees *without* allowing the process to modify its own limits. Due to
> the cgroup core restrictions and unix permission model, this allows for
> processes to create new subtrees without breaking the cgroup limits for
> the process.

I don't get why this is necessary.  What's wrong with the parent
setting up permission correctly for the namespace?

Thanks.

-- 
tejun