Synopsis

Important: kernel security and bug fix update

Type/Severity

Security Advisory: Important

Topic

Updated kernel packages that fix two security issues and three bugs are now
available for Red Hat Enterprise Linux 5.6 Extended Update Support.

The Red Hat Security Response Team has rated this update as having
important security impact. Common Vulnerability Scoring System (CVSS) base
scores, which give detailed severity ratings, are available for each
vulnerability from the CVE links in the References section.

Description

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

This update includes backported fixes for two security issues. These issues
only affected users of Red Hat Enterprise Linux 5.6 Extended Update
Support, as they have already been addressed for users of Red Hat
Enterprise Linux 5 in the 5.7 update, RHSA-2011:1065.

This update fixes the following security issues:

• A flaw was found in the way the Xen hypervisor implementation handled

instruction emulation during virtual machine exits. A malicious user-space
process running in an SMP guest could trick the emulator into reading a
different instruction than the one that caused the virtual machine to exit.
An unprivileged guest user could trigger this flaw to crash the host. This
only affects systems with both an AMD x86 processor and the AMD
Virtualization (AMD-V) extensions enabled. (CVE-2011-1780, Important)

• A flaw allowed the tc_fill_qdisc() function in the Linux kernel's packet

scheduler API implementation to be called on built-in qdisc structures. A
local, unprivileged user could use this flaw to trigger a NULL pointer
dereference, resulting in a denial of service. (CVE-2011-2525, Moderate)

This update also fixes the following bugs:

• A bug was found in the way the x86_emulate() function handled the IMUL

instruction in the Xen hypervisor. On systems without support for hardware
assisted paging (HAP), such as those running CPUs that do not have support
for (or those that have it disabled) Intel Extended Page Tables (EPT) or
AMD Virtualization (AMD-V) Rapid Virtualization Indexing (RVI), this bug
could cause fully-virtualized guests to crash or lead to silent memory
corruption. In reported cases, this issue occurred when booting
fully-virtualized Red Hat Enterprise Linux 6.1 guests with memory cgroups
enabled. (BZ#712884)

• A bug in the way the ibmvscsi driver handled interrupts may have

prevented automatic path recovery for multipath devices. This bug only
affected 64-bit PowerPC systems. (BZ#720929)

• The RHSA-2009:1243 update introduced a regression in the way file locking

on NFS (Network File System) was handled. This caused applications to hang
if they made a lock request on a file on an NFS version 2 or 3 file system
that was mounted with the "sec=krb5" option. With this update, the original
behavior of using mixed RPC authentication flavors for NFS and locking
requests has been restored. (BZ#722854)

Users should upgrade to these updated packages, which contain backported
patches to resolve 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
https://access.redhat.com/kb/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 5.6 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 5.6 ia64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 5.6 i386
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 5.6 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 5.6 i386
• Red Hat Enterprise Linux Server - AUS 5.6 x86_64
• Red Hat Enterprise Linux Server - AUS 5.6 ia64
• Red Hat Enterprise Linux Server - AUS 5.6 i386
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 5.6 s390x
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 5.6 ppc

Fixes

• BZ - 702657 - CVE-2011-1780 kernel: xen: svm: insufficiencies in handling emulated instructions during vm exits
• BZ - 712884 - RHEL6.1 32bit xen hvm guest crash randomly
• BZ - 719066 - [RHEL5.7][kernel-xen] HVM guests hang during installation on AMD systems
• BZ - 720552 - CVE-2011-2525 kernel: kernel: net_sched: fix qdisc_notify()

CVEs

• CVE-2011-2525
• CVE-2011-1780

References