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Date: Sat, 7 Mar 2015 09:09:05 -0600 (CST)
From: Christoph Lameter <cl@linux.com>
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To: "Serge E. Hallyn" <serge@hallyn.com>
cc: Andy Lutomirski <luto@amacapital.net>,
        Serge Hallyn <serge.hallyn@canonical.com>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linuxfoundation.org>,
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        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 API <linux-api@vger.kernel.org>,
        Michael Kerrisk <mtk.manpages@gmail.com>
Subject: Re: [PATCH] capabilities: Ambient capability set V2
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On Fri, 6 Mar 2015, Serge E. Hallyn wrote:

> > I think that's right.  fI doesn't set pI.
>
> Right.  The idea is that for the running binary to get capability x in its
> pP, its privileged ancestor must have set x in pI, and the binary itself
> must be trusted with x in fI.

The ancestor here is ambient_test and when it is run pI will not be set
despite the cap setting.

Therefore anything is spawns cannot have the inheritance bits set either.
This plainly does not make any sense whatsoever. If this is so as it seems
to be then we should be able to remove the inheritance bits because they
have no effect.