USN-1008-3: libvirt update

USN-1008-1 fixed vulnerabilities in libvirt. The update for Ubuntu 10.04
LTS reverted a recent bug fix update. This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

It was discovered that libvirt would probe disk backing stores without
consulting the defined format for the disk. A privileged attacker in the
guest could exploit this to read arbitrary files on the host. This issue
only affected Ubuntu 10.04 LTS. By default, guests are confined by an
AppArmor profile which provided partial protection against this flaw.
(CVE-2010-2237, CVE-2010-2238)

It was discovered that libvirt would create new VMs without setting a
backing store format. A privileged attacker in the guest could exploit this
to read arbitrary files on the host. This issue did not affect Ubuntu 8.04
LTS. In Ubuntu 9.10 and later guests are confined by an AppArmor profile
which provided partial protection against this flaw. (CVE-2010-2239)

Jeremy Nickurak discovered that libvirt created iptables rules with too
lenient mappings of source ports. A privileged attacker in the guest could
bypass intended restrictions to access privileged resources on the host.
(CVE-2010-2242)