10 - RHSA-2010:0893

Problem Description:

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.

2. Relevant releases/architectures:

Red Hat Enterprise Linux (v. 5.3.z server) - i386, ia64, noarch, ppc, s390x, x86_64

3. 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.

4. 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.

5. Bugs fixed (http://bugzilla.redhat.com/):

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