7.2 - RHSA-2011:1163

Problem Description:

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.

2. Relevant releases/architectures:

Red Hat Enterprise Linux (v. 5 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 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.

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 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.

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

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