Re: [PATCH] capabilities: Ambient capability set V1

From: "Serge E. Hallyn" <serge@hallyn.com>
To: Christoph Lameter <cl@linux.com>
Cc: Serge Hallyn <serge.hallyn@ubuntu.com>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Serge Hallyn <serge.hallyn@canonical.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Aaron Jones <aaronmdjones@gmail.com>, "Ted Ts'o" <tytso@mit.edu>,
	linux-security-module@vger.kernel.org, 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-api@vger.kernel.org,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	Jonathan Corbet <corbet@lwn.net>
Subject: Re: [PATCH] capabilities: Ambient capability set V1
Date: Thu, 26 Feb 2015 09:35:24 -0600	[thread overview]
Message-ID: <20150226153524.GC15182@mail.hallyn.com> (raw)
In-Reply-To: <alpine.DEB.2.11.1502251423580.13489@gentwo.org>

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@fujitsu-haswell:~$ su
> setgid: Operation not permitted

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

-serge