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Date: Sun, 18 Jun 2006 19:25:12 +1000
From: Nick Withers <nick@nickwithers.com>
To: "Nick Borisov" <neiro21@gmail.com>
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Cc: freebsd-security@freebsd.org
Subject: Re: memory pages nulling when releasing
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On Sun, 18 Jun 2006 12:27:22 +0400
"Nick Borisov" <neiro21@gmail.com> wrote:

> Hello everyone!
> 
> Could you tell me if FreeBSD supports memory page nulling when
> releasing it to prevent unauthorized access to data left in the page
> after it's allocated again.

I'm certainly not as expert in this area, but I thought I'd
offer the following suggestions anyway (I'm assuming you're
coding in C, here):
  - You might want to look at _malloc_options /
MALLOC_OPTIONS (for example, '_malloc_options = "J";'), though
this might be an expensive way to achieve the goal. See man 2
free for more information
  - You could zero a memory range explicitly before free()ing
it, using bzero(3) or memset(3), for instance, or even just by
assignment in some cases. This has the notable advantage that
you can hand-pick which data you're zeroing based on individual
merit

> If it does, what sys calls etc provide that?
> IMHO this is an important issue when operating data with different
> sensivity levels.
> 
> Thanks in advance.
> 
> Nick

Hope that helps!
-- 
Nick Withers
email: nick@nickwithers.com
Web: http://www.nickwithers.com
Mobile: +61 414 397 446