linux-kernel - Re: [PATCH] capabilities: Ambient capability set V2

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Date:	Mon, 2 Mar 2015 09:43:17 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	"Serge E. Hallyn" <serge@...lyn.com>
cc:	Serge Hallyn <serge.hallyn@...onical.com>,
	Andy Lutomirski <luto@...capital.net>,
	Jonathan Corbet <corbet@....net>,
	Aaron Jones <aaronmdjones@...il.com>,
	linux-security-module@...r.kernel.org,
	linux-kernel@...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-api@...r.kernel.org, Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [PATCH] capabilities: Ambient capability set V2

On Sat, 28 Feb 2015, Serge E. Hallyn wrote:

> Your example program is not filling in pI though?

The setcap sets the inheritance bit. When the binary runs the i bits
should be set.

> Ah, i see why.  In get_file_caps() you are still assigning
>
> 	fP = pA
>
> if the file has no file capabilities.  so then you are actually
> doing
>
> 	 pP' = (X & (fP | pA)) | (pI & (fI | pA))
> rather than
> 	 pP' = (X & fP) | (pI & (fI | pA))


I thought that fP, fI and pI = {} since the file has no caps
so this comes  out as

pP' = pA

> Other than that, the patch is looking good to me.  We should
> consider emitting an audit record when a task fills in its

How do I do that?

> pA, and I do still wonder whether we should be requiring
> CAP_SETFCAP (unsure how best to think of it).  But assuming the
> fP = pA was not intended, I think this largely does the right
> thing.
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