GLSA-200403-02 : Linux kernel do_mremap local privilege escalation vulnerability

This script is Copyright (C) 2004-2014 Tenable Network Security, Inc.


Synopsis :

The remote Gentoo host is missing one or more security-related
patches.

Description :

The remote host is affected by the vulnerability described in GLSA-200403-02
(Linux kernel do_mremap local privilege escalation vulnerability)

The memory subsystem allows for shrinking, growing, and moving of
chunks of memory along any of the allocated memory areas which the
kernel posesses.
To accomplish this, the do_mremap code calls the do_munmap() kernel
function to remove any old memory mappings in the new location - but,
the code doesn't check the return value of the do_munmap() function
which may fail if the maximum number of available virtual memory area
descriptors has been exceeded.
Due to the missing return value check after trying to unmap the middle
of the first memory area, the corresponding page table entries from the
second new area are inserted into the page table locations described by
the first old one, thus they are subject to page protection flags of
the first area. As a result, arbitrary code can be executed.

Impact :

Arbitrary code with normal non-super-user privelerges may be able to
exploit this vulnerability and may disrupt the operation of other parts
of the kernel memory management subroutines finally leading to
unexpected behavior.
Since no special privileges are required to use the mremap() and
mummap() system calls any process may misuse this unexpected behavior
to disrupt the kernel memory management subsystem. Proper exploitation
of this vulnerability may lead to local privilege escalation allowing
for the execution of arbitrary code with kernel level root access.
Proof-of-concept exploit code has been created and successfully tested,
permitting root escalation on vulnerable systems. As a result, all
users should upgrade their kernels to new or patched versions.

Workaround :

Users who are unable to upgrade their kernels may attempt to use
'sysctl -w vm.max_map_count=1000000', however, this is a temporary fix
which only solves the problem by increasing the number of memory areas
that can be created by each process. Because of the static nature of
this workaround, it is not recommended and users are urged to upgrade
their systems to the latest avaiable patched sources.

See also :

http://isec.pl/vulnerabilities/isec-0014-mremap-unmap.txt
http://www.gentoo.org/security/en/glsa/glsa-200403-02.xml

Solution :

Users are encouraged to upgrade to the latest available sources for
their system:
# emerge sync
# emerge -pv your-favourite-sources
# emerge your-favourite-sources
# # Follow usual procedure for compiling and installing a kernel.
# # If you use genkernel, run genkernel as you would do normally.
# # IF YOUR KERNEL IS MARKED as 'remerge required!' THEN
# # YOU SHOULD UPDATE YOUR KERNEL EVEN IF PORTAGE
# # REPORTS THAT THE SAME VERSION IS INSTALLED.

Risk factor :

High / CVSS Base Score : 7.2
(CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C)

Family: Gentoo Local Security Checks

Nessus Plugin ID: 14453 (gentoo_GLSA-200403-02.nasl)

Bugtraq ID:

CVE ID: CVE-2004-0077