linux-kernel - Re: [RFC][PATCH 2/2 v3] security: Add task_settimerslack/task

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Date:	Thu, 21 Jul 2016 21:43:26 +1000 (AEST)
From:	James Morris <jmorris@...ei.org>
To:	John Stultz <john.stultz@...aro.org>
cc:	lkml <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Oren Laadan <orenl@...lrox.com>,
	Ruchi Kandoi <kandoiruchi@...gle.com>,
	Rom Lemarchand <romlem@...roid.com>,
	Todd Kjos <tkjos@...gle.com>, Colin Cross <ccross@...roid.com>,
	Nick Kralevich <nnk@...gle.com>,
	Dmitry Shmidt <dimitrysh@...gle.com>,
	Elliott Hughes <enh@...gle.com>,
	Android Kernel Team <kernel-team@...roid.com>,
	LSM List <linux-security-module@...r.kernel.org>,
	SELinux <selinux@...ho.nsa.gov>
Subject: Re: [RFC][PATCH 2/2 v3] security: Add task_settimerslack/task_gettimerslack
 LSM hook

On Wed, 20 Jul 2016, John Stultz wrote:

> On Tue, Jul 19, 2016 at 11:12 PM, James Morris <jmorris@...ei.org> wrote:
> > On Mon, 18 Jul 2016, John Stultz wrote:
> >
> >> As requested, this patch implements a task_settimerslack and
> >> task_gettimerslack LSM hooks so that the /proc/<tid>/timerslack_ns
> >> interface can have finer grained security policies applied to it.
> >>
> >> I've kept the CAP_SYS_NICE check in the timerslack_ns_write/show
> >> functions, as hiding it in the LSM hook seems too opaque, and doesn't
> >> seem like a widely enough adopted practice.
> >>
> >
> > I may have missed something in the earlier discussion, but why do we need
> > new LSM hooks here vs. calling the existing set/getscheduler hooks?
> 
> Mostly since adding a new hook was suggested originally. I don't think
> there's much difference as it stands, but I guess more fine grained
> checks could be added on the slack amounts, etc.
> 
> I can rework it, so let me know if using the existing hooks would be
> preferred, but otherwise I'll be sending out the non-rfc patches
> tomorrow.


I'd prefer to re-use the existing hooks, unless there is a specific need 
for the extra granularity.


-- 
James Morris
<jmorris@...ei.org>