linux-kernel - Re: [PATCH 3/7] SLIM main patch

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Message-Id: <1156408305.3014.38.camel@laptopd505.fenrus.org>
Date:	Thu, 24 Aug 2006 10:31:44 +0200
From:	Arjan van de Ven <arjan@...radead.org>
To:	Kylene Jo Hall <kjhall@...ibm.com>
Cc:	Benjamin LaHaise <bcrl@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	LSM ML <linux-security-module@...r.kernel.org>,
	Dave Safford <safford@...ibm.com>,
	Mimi Zohar <zohar@...ibm.com>, Serge Hallyn <sergeh@...ibm.com>
Subject: Re: [PATCH 3/7] SLIM main patch

On Wed, 2006-08-23 at 15:20 -0700, Kylene Jo Hall wrote:
> On Wed, 2006-08-23 at 16:41 -0400, Benjamin LaHaise wrote:
> > On Wed, Aug 23, 2006 at 01:35:56PM -0700, Kylene Jo Hall wrote:
> > > Example: The current process is running at the USER level and writing to
> > > a USER file in /home/user/.  The process then attempts to read an
> > > UNTRUSTED file.  The current process will become UNTRUSTED and the read
> > > allowed to proceed but first write access to all USER files is revoked
> > > including the ones it has open.
> > 
> > Don't threads share file tables?  What is preventing malicious code from 
> > starting another thread which continues writing to the file that the 
> > revoke attempt is made on?
> 
> Well if they do share file tables then revoking write access from the
> file in the file table will revoke access for all threads.  It looks
> like sharing or copying the file table is based on a flag to the clone
> call and we are looking into whether you could exploit that situation.


well there's many corner cases; like dup2(), or sending the fd over unix
domains (and having it pending there while the revoke happens, and later
accept it)....


-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com

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