(RHSA-2011:0919) Important: qemu-kvm security and bug fix update

KVM (Kernel-based Virtual Machine) is a full virtualization solution for
Linux on AMD64 and Intel 64 systems. qemu-kvm is the user-space component
for running virtual machines using KVM.

It was found that the virtio subsystem in qemu-kvm did not properly
validate virtqueue in and out requests from the guest. A privileged guest
user could use this flaw to trigger a buffer overflow, allowing them to
crash the guest (denial of service) or, possibly, escalate their privileges
on the host. (CVE-2011-2212)

It was found that the virtio_queue_notify() function in qemu-kvm did not
perform sufficient input validation on the value later used as an index
into the array of virtqueues. An unprivileged guest user could use this
flaw to crash the guest (denial of service) or, possibly, escalate their
privileges on the host. (CVE-2011-2512)

Red Hat would like to thank Nelson Elhage for reporting CVE-2011-2212.

This update also fixes the following bug:

• A bug was found in the way vhost (in qemu-kvm) set up mappings with the
  host kernel’s vhost module. This could result in the host kernel’s vhost
  module not having a complete view of a guest system’s memory, if that guest
  had more than 4 GB of memory. Consequently, hot plugging a vhost-net
  network device and restarting the guest may have resulted in that device no
  longer working. (BZ#701771)

All users of qemu-kvm should upgrade to these updated packages, which
contain backported patches to resolve these issues. After installing this
update, shut down all running virtual machines. Once all virtual machines
have shut down, start them again for this update to take effect.