Important: xen security and bug fix update

Updated xen packages that resolve a couple of security issues and fix a bug
are now available for Red Hat Enterprise Linux 5.

This update has been rated as having important security impact by the Red
Hat Security Response Team.

The xen packages contain tools for managing the virtual machine monitor in
Red Hat Virtualization.

It was discovered that the hypervisor's para-virtualized framebuffer (PVFB)
backend failed to validate the frontend's framebuffer description properly.
This could allow a privileged user in the unprivileged domain (DomU) to
cause a denial of service, or, possibly, elevate privileges to the
privileged domain (Dom0). (CVE-2008-1952)

A flaw was found in the QEMU block format auto-detection, when running
fully-virtualized guests and using Qemu images written on removable media
(USB storage, 3.5" disks). Privileged users of such fully-virtualized
guests (DomU), with a raw-formatted disk image, were able to write a header
to that disk image describing another format. This could allow such guests
to read arbitrary files in their hypervisor's host (Dom0). (CVE-2008-1945)

Additionally, the following bug is addressed in this update:

* The qcow-create command terminated when invoked due to glibc bounds
checking on the realpath() function.

Users of xen are advised to upgrade to these updated packages, which
resolve these security issues and fix this bug.

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

This update is available via Red Hat Network. Details on how to use
the Red Hat Network to apply this update are available at
http://kbase.redhat.com/faq/FAQ_58_10188

445844 - CVE-2008-1945 qemu/kvm/xen: add image format options for USB storage and removable media
447759 - CVE-2008-1952 qemu/xen/kvm: ioemu: Fix PVFB backend to limit frame buffer size
454651 - xen: buffer overflow detected: qcow-create terminated

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-1945
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-1952
http://www.redhat.com/security/updates/classification/#important