Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932947AbcLPVQ3 (ORCPT ); Fri, 16 Dec 2016 16:16:29 -0500 Received: from mail-oi0-f45.google.com ([209.85.218.45]:33602 "EHLO mail-oi0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758892AbcLPVQR (ORCPT ); Fri, 16 Dec 2016 16:16:17 -0500 MIME-Version: 1.0 In-Reply-To: <20161216210539.GA15589@mail.hallyn.com> References: <43dcc6dc-265b-5eaf-3a70-701e05200b9f@gmail.com> <9ed6371f-3d38-45b1-a85b-1fbb3e5b4fc7@schaufler-ca.com> <7a6b5f38-de8e-d8d4-e6f7-feae3f8d192e@schaufler-ca.com> <20161216201026.GB14856@mail.hallyn.com> <20161216210539.GA15589@mail.hallyn.com> From: John Stultz Date: Fri, 16 Dec 2016 13:16:15 -0800 Message-ID: Subject: Re: RFC: capabilities(7): notes for kernel developers To: "Serge E. Hallyn" Cc: "Michael Kerrisk (man-pages)" , Casey Schaufler , James Morris , Kees Cook , Andy Lutomirski , Jann Horn , "Eric W. Biederman" , linux-man , linux-security-module , lkml , "Rafael J. Wysocki" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3151 Lines: 73 On Fri, Dec 16, 2016 at 1:05 PM, Serge E. Hallyn wrote: > Quoting John Stultz (john.stultz@linaro.org): >> On Fri, Dec 16, 2016 at 12:10 PM, Serge E. Hallyn wrote: >> > Quoting Michael Kerrisk (man-pages) (mtk.manpages@gmail.com): >> >> On 12/16/2016 01:44 AM, Casey Schaufler wrote: >> >> > On 12/15/2016 4:31 PM, John Stultz wrote: >> >> >> On Thu, Dec 15, 2016 at 12:40 PM, Casey Schaufler >> >> >> wrote: >> >> >>> On 12/15/2016 11:41 AM, Michael Kerrisk (man-pages) wrote: >> >> >>>> On 12/15/2016 05:29 PM, Casey Schaufler wrote: >> >> >>>>> CAP_WAKE_ALARM could readily be CAP_TIME. >> >> >>>> Actually, I don't quite understand what you mean with that sentence. >> >> >>>> Could you elaborate? >> >> >>> Should have said CAP_SYS_TIME >> >> >>> >> >> >>> Setting an alarm could be considered a time management function, >> >> >>> depending on what it actually does. >> >> >> Just a nit here. CAP_WAKE_ALARM is more about the privilege of waking >> >> >> a system from suspend, while CAP_SYS_TIME covers the ability to set >> >> >> the time. One wouldn't necessarily want to give applications which >> >> >> could wake a system up the capability to also set the time. >> >> > >> >> > Doesn't really matter, except that an ignorant developer >> >> > might make the mistake I did and assume that WAKE_ALARM >> >> > was somehow related to time management. If you want to use >> >> > it as an example don't let my dunderheadedness get in your >> >> > way. >> >> >> >> Actually, I decided it wasn't such a good example anyway. >> >> That capability could potentially be generic. (But it probably >> >> should better have been named something like 'CAP_WAKE_SYSTEM'.) >> > >> > How about: >> > >> > Subject: [PATCH 1/1] capabilities: alias CAP_WAKE_SYSTEM to CAP_WAKE_ALARM >> > >> > As suggested by Michael Kerrisk his is a less confusing name, and >> > this won't break any old userspace. >> > >> > Signed-off-by: Serge Hallyn >> > Cc: Michael Kerrisk >> > --- >> > include/uapi/linux/capability.h | 2 ++ >> > 1 file changed, 2 insertions(+) >> > >> > diff --git a/include/uapi/linux/capability.h b/include/uapi/linux/capability.h >> > index fd4f87d..ba972ff 100644 >> > --- a/include/uapi/linux/capability.h >> > +++ b/include/uapi/linux/capability.h >> > @@ -357,6 +357,8 @@ struct vfs_ns_cap_data { >> > >> > #define CAP_WAKE_ALARM 35 >> > >> > +#define CAP_WAKE_SYSTEM CAP_WAKE_ALARM >> > + >> >> I was thinking of the same thing. Although I might rename the >> numerical define to WAKE_SYSTEM and put WAKE_ALARM as the alias (along >> with a comment as to WAKE_ALARM being deprecated), so its more clear >> which is the one that ought to be used by new code. >> >> However, in the spirit of this thread, we might even consider >> broadening the cap silo a bit further, to something like >> CAP_WAKE_SUSPEND, such that it might also be able to cover broader PM >> actions? > > Or just CAP_UNSUSPEND? I guess I was trying to capture it could be use for actions like both waking and suspending the system. thanks -john