linux-kernel - Re: [PATCH 2/2] proc: Add /proc/<pid>/timerslack

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Message-ID: <CAGXu5jJWDs9PkAvDsByMy8Yb+98T75nBzfH4H898pCvrTEBTYw@mail.gmail.com>
Date:	Thu, 14 Jul 2016 10:56:36 -0700
From:	Kees Cook <keescook@...omium.org>
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	John Stultz <john.stultz@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Oren Laadan <orenl@...lrox.com>,
	Ruchi Kandoi <kandoiruchi@...gle.com>,
	Rom Lemarchand <romlem@...roid.com>,
	Android Kernel Team <kernel-team@...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>
Subject: Re: [PATCH 2/2] proc: Add /proc/<pid>/timerslack_ns interface

On Thu, Jul 14, 2016 at 10:49 AM, Serge E. Hallyn <serge@...lyn.com> wrote:
> Kees, you said adding a capability is hard - can you expound on that?

Best I can find at the moment was discussion around CAP_COMPROMISE_KERNEL:
http://thread.gmane.org/gmane.linux.kernel/1459165

Basically, adding a new capability for an interface can create
userspace compatibility problems (though perhaps in this case, it's a
new interface, so a new capability would be okay, but it's such a
narrow use-case and CAP_SYS_NICE fits fine).

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security