KVM 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 or, possibly, escalate their privileges on the host. 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 or, possibly, escalate their privileges on the host. 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 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. 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.