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. A heap overflow flaw was found in the way QEMU-KVM emulated the e1000 network interface card. A privileged guest user in a virtual machine whose network interface is configured to use the e1000 emulated driver could use this flaw to crash the host or, possibly, escalate their privileges on the host. Red Hat would like to thank Nicolae Mogoreanu for reporting this issue. This update also fixes the following bug: * qemu-kvm has a scsi option, to be used, for example, with the -device option: -device virtio-blk-pci,drive=[drive name],scsi=off. Previously, however, it only masked the feature bit, and did not reject SCSI commands if a malicious guest ignored the feature bit and issued a request. This update corrects this issue. The scsi=off option can be used to mitigate the virtualization aspect of CVE-2011-4127 before the RHSA-2011:1849 kernel update is installed on the host. This mitigation is only required if you do not have the RHSA-2011:1849 kernel update installed on the host and you are using raw format virtio disks backed by a partition or LVM volume. If you run guests by invoking /usr/libexec/qemu-kvm directly, use the -global virtio-blk-pci.scsi=off option to apply the mitigation. If you are using libvirt, as recommended by Red Hat, and have the RHBA-2012:0013 libvirt update installed, no manual action is required: guests will automatically use scsi=off. Note: After installing the RHSA-2011:1849 kernel update, SCSI requests issued by guests via the SG_IO IOCTL will not be passed to the underlying block device when using raw format virtio disks backed by a partition or LVM volume, even if scsi=on is used. As well, this update adds the following enhancement: * Prior to this update, qemu-kvm was not built with RELRO or PIE support. qemu-kvm is now built with full RELRO and PIE support as a security enhancement. All users of qemu-kvm should upgrade to these updated packages, which correct these issues and add this enhancement. 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.