linux-kernel - Re: [RFC] cgroups: implement device whitelist lsm (v2)

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Date:	Fri, 14 Mar 2008 02:16:46 -0700
From:	"Paul Menage" <menage@...gle.com>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	linux-security-module@...r.kernel.org, "Greg KH" <greg@...ah.com>,
	"Stephen Smalley" <sds@...ch.ncsc.mil>,
	"Casey Schaufler" <casey@...aufler-ca.com>,
	"Pavel Emelianov" <xemul@...nvz.org>
Subject: Re: [RFC] cgroups: implement device whitelist lsm (v2)

On Wed, Mar 12, 2008 at 8:27 PM, Serge E. Hallyn <serue@...ibm.com> wrote:
>
>  While composing this with the ns_cgroup may seem logical, it is not
>  the right thing to do, because updates to /cg/cg1/devcg.deny are
>  not reflected in /cg/cg1/cg2/devcg.allow.

Maybe you should follow up the tree to ensure that all parent groups
have access to the device too? Or alternatively, cache the results of
this lookup whenever permissions for a device change?

>
>  A task may only be moved to another devcgroup if it is moving to
>  a direct descendent of its current devcgroup.

What's the rationale for that?

>
>  CAP_NS_OVERRIDE is defined as the capability needed to cross namespaces.
>  A task needs both CAP_NS_OVERRIDE and CAP_SYS_ADMIN to create a new
>  devcgroup, update a devcgroup's access, or move a task to a new
>  devcgroup.

But this isn't necessarily crossing namespaces. It could be used for
device control in the same namespace (e.g. allowing a job to access a
raw disk for its data storage rather than going through the
filesystem).

Paul
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