linux-kernel - Re: [patch 2/3] MAP_NOZERO

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Date:	Wed, 27 Jun 2007 19:58:09 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Nicholas Miell <nmiell@...cast.net>
cc:	Hugh Dickins <hugh@...itas.com>,
	Ulrich Drepper <drepper@...il.com>, blaisorblade@...oo.it,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [patch 2/3] MAP_NOZERO - implement sys_brk2()

On Wed, 27 Jun 2007, Davide Libenzi wrote:

> On Wed, 27 Jun 2007, Nicholas Miell wrote:
> 
> > 1) euid is not sufficient, you need to store away arbitrary LSM
> > information and call LSM hooks to decide security equivalence. The same
> > applies to VServer or whatever other container system you use.
> 
> The EUID that is used now, can easily be any cookie. It can be an LSM 
> cookie (if LSM is active in the system). We don't do complex checks, like 
> group permission & Co.  We assume that if a UID-cookie had such data 
> available (or it generated it), it can have it back uncleared.

(looking through the LSM/SeLinux jungle)
Also, LSM/SeLinux could disable completely the feature, at request. Just 
assign a known-to-be-invalid UID to mm->owner_uid (passign through 
an(other) hook), and pages will never be recycled.



- Davide


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