linux-kernel - Re: [PATCH] capabilities: Ambient capability set V1

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Message-ID: <20150226153524.GC15182@mail.hallyn.com>
Date:	Thu, 26 Feb 2015 09:35:24 -0600
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Serge Hallyn <serge.hallyn@...ntu.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Andy Lutomirski <luto@...capital.net>,
	Aaron Jones <aaronmdjones@...il.com>, Ted Ts'o <tytso@....edu>,
	linux-security-module@...r.kernel.org, akpm@...uxfoundation.org,
	"Andrew G. Morgan" <morgan@...nel.org>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Austin S Hemmelgarn <ahferroin7@...il.com>,
	Markku Savela <msa@...h.iki.fi>,
	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH] capabilities: Ambient capability set V1

On Wed, Feb 25, 2015 at 02:25:19PM -0600, Christoph Lameter wrote:
> On Wed, 25 Feb 2015, Serge Hallyn wrote:
> 
> > Yeah we could make this
> 
> 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

> Its best to leave perm bits untouched.


> christoph@...itsu-haswell:~$ su
> setgid: Operation not permitted

Did you initialize by running a program to fill your pI?

-serge
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