EGI CSIRT:Alerts/rds-2010-10-18

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EGI CSIRT ADVISORY [EGI-ADV-20101020]

Title:  HIGH Local root vulnerability in RDS (CVE-2010-3904) [EGI-ADV-20101020]
Date: October 20, 2010
URL:  https://wiki.egi.eu/wiki/EGI_CSIRT:Alerts/rds-2010-10-18

Introduction
============

Yesterday, Dan Rosenberg released information about a vulnerability in
the RDS module in the Linux kernel, complete with an exploit that on
many systems can give any local user root privileges.

This vulnerability has been labelled CVE-2010-3904, and is present on
many Linux distributions, including RHEL/CentOS/SL 5 (but *not* RHEL 3
and 4 and their derivatives). Vendor patches are not yet available.

Details
=======

The RDS module, when communicating over an RDS socket, performs
insufficient access permission checks, which lets an attacker
overwrite arbitrary kernel memory. This is easily exploited to give
root privileges.

Please note that the proof-of-concept exploit included in Rosenberg's
advisory does not work on RHEL 5 derivatives because of certain
implementation details, but the vulnerability *is* still present and
easily exploited.

However EGI CSIRT does have a working unpublished exploit code for
RHEL5.


Mitigation
==========

Most systems do not utilize RDS and can simply block the vulnerability
by blacklisting the RDS module (after unloading it if it is present),
for instance by running this script:

------------------
 
#!/bin/sh

# Unload the module

if lsmod | grep -q '^rds '; then
  echo "RDS was loaded"
fi
rmmod rds 2>/dev/null
if lsmod | grep -q '^rds '; then
  echo "FAILED to unload RDS"
fi

# Blacklist the module
echo "install rds /bin/true" > /etc/modprobe.d/disable-rds 
 
echo "alias net-pf-28 off" > /etc/modprobe.d/disable-rds

------------------

This will take effect immediately and does not require a reboot. The
blacklisting will stay persistent across reboots.

Please note that some clusters with Infiniband may actually use RDS.
In these cases, the only solution is to deploy a patched kernel.

 
Recommendations
===============

Immediately apply the mitigation described above to all
user-accessible systems.

Apply vendor kernel updates when they become available.


References
==========

Rosenberg's advisory:
http://www.vsecurity.com/resources/advisory/20101019-1/
 
RedHat Bugzilla:
https://bugzilla.redhat.com/show_bug.cgi?id=642896