Red Hat: RHSA-2010:0126-01 Critical KVM Privilege Escalation Advisory

KVM (Kernel-based Virtual Machine) is a full virtualization solution for Linux on AMD64 and Intel 64 systems. KVM is a Linux kernel module built for the standard Red Hat Enterprise Linux kernel.
A flaw was found in the way the x86 emulator loaded segment selectors (used for memory segmentation and protection) into segment registers. In some guest system configurations, an unprivileged guest user could leverage this flaw to crash the guest or possibly escalate their privileges within the guest. (CVE-2010-0419)
The x86 emulator implementation was missing a check for the Current Privilege Level (CPL) while accessing debug registers. An unprivileged user in a guest could leverage this flaw to crash the guest. (CVE-2009-3722)
This update also fixes the following bugs:
With Red Hat Enterprise Virtualization, the virtio_blk_dma_restart_bh() function was previously used to handle write errors; however, a bug fix provided by the RHSA-2009:1659 update meant that read errors would also have to be handled by this function. The function was not updated for this, causing read errors to be resubmitted as writes. This caused guest image corruption in some cases.
Additionally, the return values of the bdrv_aio_write() and bdrv_aio_read() functions were ignored. If an immediate failure occurred in one of these functions, errors would be missed and the guest could hang or read corrupted data. (BZ#562776)
All KVM users should upgrade to these updated packages, which contain backported patches to resolve these issues. Note: The procedure in the Solution section must be performed before this update will take effect.