[32722] in bugtraq
Re: Hot fix for do_brk bug
daemon@ATHENA.MIT.EDU (Goetz Babin-Ebell)
Fri Dec 5 17:27:31 2003
Message-ID: <3FD0F92F.6090909@trustcenter.de>
Date: Fri, 05 Dec 2003 22:31:27 +0100
From: Goetz Babin-Ebell <babin-ebell@trustcenter.de>
MIME-Version: 1.0
To: bugtraq@securityfocus.com
In-Reply-To: <200312042341.hB4Nfbmd005154@pookie.nersc.gov>
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Hello Shane,
canon@nersc.gov wrote:
> I've written a linux kernel module that can be used to hot fix a
> Linux system for the bug in do_brk. It scans the
> kernel space and replaces jmp and calls to do_brk
> to point to a wrapper routine instead. It also maps
> the symbol table to point to the wrapper. This only
> works on x86 and it has only been tested with RH kernels
> 2.4.18-27.7.xsmp and 2.4.20-20.7smp. It is quite possible
> this could crash or screw-up a system, so use at your own
> risk. I've tested the module against the proof of concept code
> written and posted by Christophe Devine. The module catches
> the exploit and logs the attempt.
It would be less intrusive to the kernel to supply a fixed do_brk()
and replace the do_brk with a jump to your version.
This way you only have to touch one place
in the kernel space (and no guesswork, no modify
of kernel data that might look like a pointer to do_brk()
but is really something else...)
Bye
Goetz
--
Goetz Babin-Ebell, TC TrustCenter AG, http://www.trustcenter.de
Sonninstr. 24-28, 20097 Hamburg, Germany
Tel.: +49-(0)40 80 80 26 -0, Fax: +49-(0)40 80 80 26 -126
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