linux-kernel - Re: Controlling devices and device namespaces

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Date:	Sun, 16 Sep 2012 05:17:44 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	Aristeu Rozanski <aris@...vo.org>,
	Neil Horman <nhorman@...driver.com>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...e.cz>,
	Thomas Graf <tgraf@...g.ch>, Paul Mackerras <paulus@...ba.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Johannes Weiner <hannes@...xchg.org>,
	Tejun Heo <tj@...nel.org>, cgroups@...r.kernel.org,
	Paul Turner <pjt@...gle.com>, Ingo Molnar <mingo@...hat.com>
Subject: Re: Controlling devices and device namespaces

ebiederm@...ssion.com (Eric W. Biederman) writes:

> Alan Cox <alan@...rguk.ukuu.org.uk> writes:
>
>>> One piece of the puzzle is that we should be able to allow unprivileged
>>> device node creation and access for any device on any filesystem
>>> for which it unprivileged access is safe.
>>
>> Which devices are "safe" is policy for all interesting and useful cases,
>> as are file permissions, security tags, chroot considerations and the
>> like.
>>
>> It's a complete non starter.

Come to think of it mknod is completely unnecessary.

Without mknod.  Without being able to mount filesystems containing
device nodes.  The mount namespace is sufficient to prevent all of the
cases that the device control group prevents (open and mknod on device
nodes).

So I honestly think the device control group is superflous, and it is
probably wise to deprecate it and move to a model where it does not
exist.

Eric
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