From owner-freebsd-security@FreeBSD.ORG  Sun Apr 20 18:31:16 2014
Return-Path: <owner-freebsd-security@FreeBSD.ORG>
Delivered-To: freebsd-security@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id C32D8F2C
 for <freebsd-security@freebsd.org>; Sun, 20 Apr 2014 18:31:16 +0000 (UTC)
Received: from pacha.mail.dyslexicfish.net (space.mail.dyslexicfish.net
 [91.109.5.35])
 (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id 5DDE21760
 for <freebsd-security@freebsd.org>; Sun, 20 Apr 2014 18:31:16 +0000 (UTC)
Received: from catnip.dyslexicfish.net (space.mail.dyslexicfish.net
 [91.109.5.35])
 by pacha.mail.dyslexicfish.net (8.14.5/8.14.5) with ESMTP id s3KIVCNt054779;
 Sun, 20 Apr 2014 19:31:13 +0100 (BST)
 (envelope-from jamie@catnip.dyslexicfish.net)
Received: (from jamie@localhost)
 by catnip.dyslexicfish.net (8.14.5/8.14.5/Submit) id s3KIVCSY054778;
 Sun, 20 Apr 2014 19:31:12 +0100 (BST) (envelope-from jamie)
From: Jamie Landeg-Jones <jamie@dyslexicfish.net>
Message-Id: <201404201831.s3KIVCSY054778@catnip.dyslexicfish.net>
Date: Sun, 20 Apr 2014 19:31:12 +0100
To: hcoin@quietfountain.com, freebsd-security@freebsd.org
Subject: Re: De Raadt + FBSD + OpenSSH + hole?
References: <534B11F0.9040400@paladin.bulgarpress.com>
 <201404141207.s3EC7IvT085450@chronos.org.uk>
 <201404141232.s3ECWFQ1081178@catnip.dyslexicfish.net>
 <53522186.9030207@FreeBSD.org>
 <201404200548.s3K5mV7N055244@catnip.dyslexicfish.net>
 <53540307.1070708@quietfountain.com>
In-Reply-To: <53540307.1070708@quietfountain.com>
User-Agent: Heirloom mailx 12.4 7/29/08
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7
 (pacha.mail.dyslexicfish.net [91.109.5.35]);
 Sun, 20 Apr 2014 19:31:13 +0100 (BST)
X-BeenThere: freebsd-security@freebsd.org
X-Mailman-Version: 2.1.17
Precedence: list
List-Id: "Security issues \[members-only posting\]"
 <freebsd-security.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-security>, 
 <mailto:freebsd-security-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-security/>
List-Post: <mailto:freebsd-security@freebsd.org>
List-Help: <mailto:freebsd-security-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-security>, 
 <mailto:freebsd-security-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 20 Apr 2014 18:31:16 -0000

> I wonder how many security holes, both those known and as yet unrevealed 
> or unknown, would not be of any exploit value if in all security related 
> libraries and applications the routine to free allocated memory 
> allocation closest to the user app/library  set the newly free memory to 
> a known pattern or something from /dev/random before returning.  And, 
> similarly, a compiler option causing function returns using more than a 
> few dozen bytes of stack space to erase the newly freed stack region 

I'm probably being really dense here, and realise I can't delete this
post once sent! But....

Once memory has been freed, I thought any attempt by a user process to
access it would cause a SIGSEV.

I thought the issue was with programs that inadvertantly expose (either
to read or write) other parts of their active memory.

Of course, if a process rolls it's own in-process implementation
of malloc/free, then this point is moot, but once you free memory back
to the system, isn't in no longer accessable anyway?

Cheers,
       Jamie