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Re: Linux kernel file offset pointer races


From: Andrew Farmer <andfarm () teknovis com>
Date: Wed, 4 Aug 2004 15:42:13 -0700

On 4 Aug 2004, at 03:22, Paul Starzetz wrote:
Synopsis:  Linux kernel file offset pointer handling
Product:   Linux kernel
Version:   2.4 up to to and including 2.4.26, 2.6 up to to and
           including 2.6.7
Vendor:    http://www.kernel.org/
URL:       http://isec.pl/vulnerabilities/isec-0016-procleaks.txt
CVE:       CAN-2004-0415
Author:    Paul Starzetz <ihaquer () isec pl>
Date:      Aug 04, 2004


Issue:
======

A critical security vulnerability has been found in the Linux kernel
code handling 64bit file offset pointers.
...

Even discounting the mangling in this posting, the code doesn't work
as advertised under 2.6.7. I've tried a number of different scenarios:
multiple machines, slow storage, fast storage, large files, small files - but _llseek(pfd, 0, 0, &off, SEEK_CUR) doesn't fail. Is this just because
I'm stupid or because the code supplied is incorrect?

Furthermore, mtrr_read doesn't seem to exist anywhere in the Linux kernel,
at least not by that name. The function in question would probably exist
in linux/arch/i386/kernel/cpu/mtrr/if.c, but there's nothing of the sort
in there. Heck, the kernel code shown isn't even VALID.

My fault or Paul's?

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