RHSA-2010:0893 - Security Advisory

Topic

Updated kernel packages that fix one security issue and three bugs are now
available for Red Hat Enterprise Linux 5.3 Extended Update Support.

The Red Hat Security Response Team has rated this update as having
important security impact. A Common Vulnerability Scoring System (CVSS)
base score, which gives a detailed severity rating, is available from the
CVE link in the References section.

Description

The kernel packages contain the Linux kernel, the core of any Linux
operating system.

This update fixes the following security issue:

• Buffer overflow flaws were found in the Linux kernel's implementation of

the server-side External Data Representation (XDR) for the Network File
System (NFS) version 4. An attacker on the local network could send a
specially-crafted large compound request to the NFSv4 server, which could
possibly result in a kernel panic (denial of service) or, potentially, code
execution. (CVE-2010-2521, Important)

This update also fixes the following bugs:

• A race condition existed when generating new process IDs with the result

that the wrong process could have been signaled or killed accidentally,
leading to various application faults. This update detects and disallows
the reuse of PID numbers. (BZ#638864)

• When multiple JBD-based (Journaling Block Device) file systems were

mounted concurrently, and no other JBD-based file systems were already
mounted, a race could occur between JBD slab cache creation and deletion.
(BZ#645653)

• A missing memory barrier caused a race condition in the AIO subsystem

between the read_events() and aio_complete() functions. This may have
caused a thread in read_events() to sleep indefinitely, possibly causing an
application hang. (BZ#638868)

Users should upgrade to these updated packages, which contain backported
patches to correct these issues. The system must be rebooted for this
update to take effect.

Solution

Before applying this update, make sure all previously-released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
http://kbase.redhat.com/faq/docs/DOC-11259

To install kernel packages manually, use "rpm -ivh [package]". Do not
use "rpm -Uvh" as that will remove the running kernel binaries from
your system. You may use "rpm -e" to remove old kernels after
determining that the new kernel functions properly on your system.

Affected Products

• Red Hat Enterprise Linux for x86_64 - Extended Update Support 5.3 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 5.3 ia64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 5.3 i386
• Red Hat Enterprise Linux Server - AUS 5.3 x86_64
• Red Hat Enterprise Linux Server - AUS 5.3 ia64
• Red Hat Enterprise Linux Server - AUS 5.3 i386
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 5.3 s390x
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 5.3 ppc

Fixes

• BZ - 612028 - CVE-2010-2521 kernel: nfsd4: bug in read_buf
• BZ - 638864 - [5.5] a race in pid generation that causes pids to be reused immediately. [rhel-5.3.z]
• BZ - 638868 - race in aio_complete() leads to process hang [rhel-5.3.z]
• BZ - 645653 - [Patch] jbd slab cache creation/deletion is racey [rhel-5.3.z]

CVEs

• CVE-2010-2521

References

• http://www.redhat.com/security/updates/classification/#important