[34744] in bugtraq
Re: http://www.smashguard.org
daemon@ATHENA.MIT.EDU (Crispin Cowan)
Fri Apr 30 20:19:08 2004
Message-ID: <40918E98.8080502@immunix.com>
Date: Thu, 29 Apr 2004 16:24:08 -0700
From: Crispin Cowan <crispin@immunix.com>
MIME-Version: 1.0
To: Pavel Machek <pavel@ucw.cz>
Cc: Hilmi Ozdoganoglu <cyprian@purdue.edu>, Dave Paris <dparis@w3works.com>,
bugtraq@securityfocus.com
In-Reply-To: <20040429215507.GA22284@elf.ucw.cz>
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Pavel Machek wrote:
>>>The idea is not to create "custom CPUs" but to have our modification
>>>picked up by major vendors. Clearly there is interest in applying
>>>hardware to solve security issues based on the latest press releases
>>>
>>>
>>>from AMD that AMD chips include buffer-overflow protection (see
>>
>>
>>>Computer World, January 15, 2004).
>>>
>>>
>>>
>>As Theo said, the AMD buffer overflow "protection" is nothing more than
>>sensible separation of R and X bits per page, fixing a glaring and
>>
>>
>
>Actually it is not "sensible", and it is not separation.
>
>You can have r--, r-x, but you can't have --x.
>
>
But that is *exactly* what is meant by "separation" of R and X.
I have no idea what you mean by it not being "sensible". Most every CPU
I have ever seen does this except the x86. Someone apparently thought
there was no value in separate R and X bits for the i386 back in the
mid-80s. It was a false economy :)
Crispin
--
Crispin Cowan, Ph.D. http://immunix.com/~crispin/
CTO, Immunix http://immunix.com
Immunix 7.3 http://www.immunix.com/shop/
