linux-kernel - Re: [patch 0/4] MAP_NOZERO v2 - VM_NOZERO/MAP

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Message-ID: <Pine.LNX.4.64.0707021540560.14774@alien.or.mcafeemobile.com>
Date:	Mon, 2 Jul 2007 15:46:02 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Ulrich Drepper <drepper@...il.com>
cc:	Rik van Riel <riel@...hat.com>, Andy Isaacson <adi@...apodia.org>,
	Kyle Moffett <mrmacman_g4@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [patch 0/4] MAP_NOZERO v2 - VM_NOZERO/MAP_NOZERO early summer
 madness

On Mon, 2 Jul 2007, Ulrich Drepper wrote:

> On 7/2/07, Rik van Riel <riel@...hat.com> wrote:
> > That should not happen.  The default SELinux configuration
> > in Fedora (and Debian?) runs a few daemons in their own
> > restricted modes and has most of the system running in
> > unconfined_t, including the majority of user programs.
> 
> This is the state as of F7.  This will change hopefully soon.
> Programs like firefox run by normal users must be confined, to. Any
> tests using security must be fast, it's not something which is done
> only for a few apps.

The strong requirement would be that the cookie is not a bit longer than 
sizeof(unsigned long).
For the "equality" check, this better be "==", although it could be 
abstracted in a function/macro that SeLinux implements in a different way.
But this "equality" check is done a page-fault time, so it better be 
pretty quick (otherwise if they bloat that path, they probably be better 
of not using MAP_NOZERO at all).



- Davide


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