full-disclosure - Linux 2.6.x fs/pipe.c local root exploit (CVE-2009-3547)

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Date: Sat, 07 Nov 2009 20:37:13 +0100
From: "Edward D. Teach" <teach@...ell.org>
To: Full disclosure <full-disclosure@...ts.grok.org.uk>
Subject: Linux 2.6.x fs/pipe.c local root exploit
	(CVE-2009-3547)

For those who were not yet aware, there is at least 3 public exploits
since 11/05/2009 for CVE-2009-3547 targeting *all* linux kernels from
2.6.0 to 2.6.31 included. Since spender and fotis have already release
their own, there is not need for us to keep this on our hd. 
ImpelDown.c is a poc trying to exploit null ptr dereference in fs/pipe.c
for *all* linux kernel from 2.6.0 to 2.6.31 and ImpelDown-2.6.31only.c
target only linux kernel version 2.6.31 (tested and approuved with
mmap_min_addr at 0).
If you were writing your own, you have already noticed that there is a
subtle difference in the way you can own kernels 2.6.0 up to 2.6.10 and
kernels 2.6.11 up to 2.6.31: in the first one the null ptr deref leads
to an arbitrary write to everywhere in the kernel since you have control
over the destination address of 

linux2.6.9/fs/pipe.c

...
219                        if (pipe_iov_copy_from_user(pipebuf, iov, chars)) {
...
In such case, we try to exploit this by overwriting and old and obsolete 
syscall address in the sys_call_table by our privilege escalator function 
address (hehe old school trickz are always the best).

In kernels 2.6.11 up to 2.6.31, exploitation simply resume in mapping the correct 
struct pipe_inode_info at NULL and the kernel will call a fptr under our control
at inode->i_pipe->bufs[1-16].ops->something()

You can find exploits at
http://www.vxhell.org/~teach/exploits/ImpelDown.c
and
http://www.vxhell.org/~teach/exploits/ImpelDown-2.6.31only.c
The first one wasn't tested but the second would work for the given kernel 
(according to your mmap_min_addr)

We highly recommand to apply grsecurity patch ([1]) since UDEREF will preserve
you from all this bug class, 
or at least have a kernel which correctly implement mmap_min_addr, but 
Julien and Tavis [2] have already showed you how this can be easily bypassed.
Regards

[1] http://grsecurity.net 
[2] http://blog.cr0.org/2009/06/bypassing-linux-null-pointer.html

teach@...ckpearl$ head -n 18 exploits/ImpelDown-2.6.31only.c 
/******************************************************************************
 *                            .:: Impel Down ::.
 *
 *     Linux 2.6.x fs/pipe.c local kernel root(kit?) exploit (x86)
 *                              by teach & xipe
 *    Greetz goes to all our mates from #nibbles, #oldschool and
#carib0u
 *    (hehe guyz, we would probably be high profile and mediatised el8
if we 
 *    lost less time on trolling all day long, but we LOVE IT :))) 
 *    Special thanks to Ivanlef0u, j0rn & pouik for being such amazing
(but i
 *    promise ivan, one day i'll kill u :p)
 *                
 * (C) COPYRIGHT teach & xipe, 2009
 * All Rights Reserved
 *
 * teach@...ell.org
 * xipe@...ell.org
 *    

*******************************************************************************/

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