From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1754333AbbBZTiY (ORCPT <rfc822;w@1wt.eu>);
	Thu, 26 Feb 2015 14:38:24 -0500
Received: from mail-lb0-f178.google.com ([209.85.217.178]:34119 "EHLO
	mail-lb0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1753551AbbBZTiX (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 26 Feb 2015 14:38:23 -0500
MIME-Version: 1.0
In-Reply-To: <20150226193200.GA17709@mail.hallyn.com>
References: <20150223181553.GE25477@ubuntumail> <20150224051928.GA14755@mail.hallyn.com>
 <20150224154715.GA20682@mail.hallyn.com> <alpine.DEB.2.11.1502240956400.29006@gentwo.org>
 <20150224164429.GB29685@ubuntumail> <alpine.DEB.2.11.1502241120270.29416@gentwo.org>
 <20150225033247.GC29685@ubuntumail> <alpine.DEB.2.11.1502251423580.13489@gentwo.org>
 <20150226153524.GC15182@mail.hallyn.com> <alpine.DEB.2.11.1502261224580.7451@gentwo.org>
 <20150226193200.GA17709@mail.hallyn.com>
From: Andy Lutomirski <luto@amacapital.net>
Date: Thu, 26 Feb 2015 11:38:01 -0800
Message-ID: <CALCETrWpKiurZEEOT25i_xrtQyk5dht+wjUO4+tGs+N_7JCdYA@mail.gmail.com>
Subject: Re: [PATCH] capabilities: Ambient capability set V1
To: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Christoph Lameter <cl@linux.com>, Serge Hallyn <serge.hallyn@ubuntu.com>,
        Serge Hallyn <serge.hallyn@canonical.com>,
        Aaron Jones <aaronmdjones@gmail.com>, "Ted Ts'o" <tytso@mit.edu>,
        LSM List <linux-security-module@vger.kernel.org>,
        Andrew Morton <akpm@linuxfoundation.org>,
        "Andrew G. Morgan" <morgan@kernel.org>,
        Mimi Zohar <zohar@linux.vnet.ibm.com>,
        Austin S Hemmelgarn <ahferroin7@gmail.com>,
        Markku Savela <msa@moth.iki.fi>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Jonathan Corbet <corbet@lwn.net>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, Feb 26, 2015 at 11:32 AM, Serge E. Hallyn <serge@hallyn.com> wrote:
> On Thu, Feb 26, 2015 at 12:28:30PM -0600, Christoph Lameter wrote:
>> On Thu, 26 Feb 2015, Serge E. Hallyn wrote:
>>
>> > > Well doing that breaks su.
>> >
>> > Don't what exactly?  You're saying that doing
>> >
>> > pI' = pI
>> > pA' = pA  (pA is ambient)
>> > pP' = (X & fP) | (pI & (fI | pA))
>> > pE' = pP' & (fE | pA)
>> >
>> > stopped su from having CAP_SETGID while
>> >
>> > pI' = pI
>> > pA' = pA  (pA is ambient)
>> > pP' = (X & fP) | (pI & (fI | pA))
>> > pE' = pP' & fE
>> >
>> > worked?  I'll hope you're saying both "fail", in which case
>>
>> fE does not exist in cpu_vfs_cap_data. We only get fI and fP. Why in the
>> world does setcap allow setting fE?
>
> It sets a bit in the magic_etc.  So fE is either all on or all off.
>
>> V1 does not use fE. In my newer attempt, I seemed to have worked
>> with zeroed field that I assumed was filled in.
>>
>> I will just do
>>
>> pE' = pP'
>>
>> Ok?
>
> Andrew Morgan was against that.  What if we changed
>
> pE' = pP' & (fE | pA)
>
> to
>
>         if (pA)
>                 pE' = pP' & fE
>         else
>                 pE' = pP'
>

Is this backwards?

Also, on further bikeshedding consideration, I think I like the name
"persistent" much better than "ambient".  Alas, "persistent" starts
with a P.

--Andy