[SECURITY-L] Nova vulnerabilidade afetando kernel 2.2, 2.4 e 2.6

[Security Team - UNICAMP]

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From: Caio Souza Mendes <caio_sm em yahoo.com.br>
Subject: Nova vulnerabilidade afetando kernel 2.2, 2.4 e 2.6
To: security em unicamp.br
Date: Mon, 5 Jan 2004 12:11:41 -0300 (ART)

Nova vulnerabilidade afetando kernel 2.2, 2.4 e 2.6
Enviado em: Monday, January 05 @ 11:21:10 EDT
Uma nova vulnerabilidade afetando as versões 2.2, 2.4
e 2.6 do kernel Linux foi anunciada por Paul Starzetz
e Wojciech Purczynski... A vulnerabilidade está
relacionada ao gerenciamento de memória pelo system
call mremap(2)... Apesar de não ser trivial, a
exploração pode levar à escalada de privilégio
localmente ou à execução de comandos arbitrários...
Algumas distribuições já estão liberando
atualizações... Leia o advisory completo logo
abaixo...



Synopsis: Linux kernel do_mremap local privilege
escalation vulnerability Product: Linux kernel
Version: 2.2, 2.4 and 2.6 series Vendor:
http://www.kernel.org/ URL:
http://isec.pl/vulnerabilities/isec-0012-mremap.txt
CVE:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2003-0985
Author: Paul Starzetz , Wojciech Purczynski Date:
January 5, 2004 Issue: ====== A critical security
vulnerability has been found in the Linux kernel
memory management code in mremap(2) system call due to
incorrect bound checks. Details: ======== The mremap
system call provides functionality of resizing
(shrinking or growing) as well as moving across
process's addressable space of exist­ ing virtual
memory areas (VMAs) or any of its parts. A typical VMA
covers at least one memory page (which is exactly 4kB
on the i386 architecture). An incorrect bound check
discovered inside the do_mremap() kernel code
performing remapping of a virtual memory area may lead
to creation of a virtual memory area of 0 bytes
length. The problem bases on the general mremap flaw
that remapping of 2 pages from inside a VMA creates a
memory hole of only one page in length but an
additional VMA of two pages. In the case of a zero
sized remapping request no VMA hole is created but an
additional VMA descriptor of 0 bytes in length is
created. Such a malicious virtual memory area may
disrupt the operation of other parts of the kernel
memory management subroutines finally leading to un­
expected behavior. A typical process's memory layout
showing invalid VMA created with mremap system call:
08048000-0804c000 r-xp 00000000 03:05 959142 /tmp/test
0804c000-0804d000 rw-p 00003000 03:05 959142 /tmp/test
0804d000-0804e000 rwxp 00000000 00:00 0
40000000-40014000 r-xp 00000000 03:05 1544523
/lib/ld-2.3.2.so 40014000-40015000 rw-p 00013000 03:05
1544523 /lib/ld-2.3.2.so 40015000-40016000 rw-p
00000000 00:00 0 4002c000-40158000 r-xp 00000000 03:05
1544529 /lib/libc.so.6 40158000-4015d000 rw-p 0012b000
03:05 1544529 /lib/libc.so.6 4015d000-4015f000 rw-p
00000000 00:00 0 [*] 60000000-60000000 rwxp 00000000
00:00 0 bfffe000-c0000000 rwxp fffff000 00:00 0 The
broken VMA in the above example has been marked with a
[*]. Impact: ======= Since no special privileges are
required to use the mremap(2) system call any process
may misuse its unexpected behavior to disrupt the ker­
nel memory management subsystem. Proper exploitation
of this vulnerabil­ ity may lead to local privilege
escalation including execution of arbi­ trary code
with kernel level access. Proof-of-concept exploit
code has been created and successfully tested giving
UID 0 shell on vulnerable systems. The exploitability
of the discovered vulnerability is possible, although
not a trivial one. We have identified at least two
different attack vec­ tors for the 2.4 kernel series.
All users are encouraged to patch all vulnerable
systems as soon as appropriate vendor patches are
released. Credits: ======== Paul Starzetz has
identified the vulnerability and performed further
research. COPYING, DISTRIBUTION, AND MODIFICATION OF
INFORMATION PRESENTED HERE IS ALLOWED ONLY WITH
EXPRESS PERMISSION OF ONE OF THE AUTHORS. Disclaimer:
=========== This document and all the information it
contains are provided "as is", for educational
purposes only, without warranty of any kind, whether
ex­ press or implied. The authors reserve the right
not to be responsible for the topicality, correctness,
completeness or quality of the information provided in
this document. Liability claims regarding damage
caused by the use of any information provided,
including any kind of information which is in­
complete or incorrect, will therefore be rejected. 


- -- 
Paul Starzetz 
iSEC Security Research 
http://isec.pl/ 

Fonte: http://www.linuxsecurity.com.br/article.php?sid=8150&mode=thread&order=0

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