6.6 - RHSA-2010:0627

Problem Description:

Updated kvm packages that fix three security issues and multiple bugs are now available for Red Hat Enterprise Linux 5.

The Red Hat Security Response Team has rated this update as having important security impact. Common Vulnerability Scoring System (CVSS) base scores, which give detailed severity ratings, are available for each vulnerability from the CVE links in the References section.

2. Relevant releases/architectures:

RHEL Desktop Multi OS (v. 5 client) - x86_64 RHEL Virtualization (v. 5 server) - x86_64

3. Description:

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.

It was found that QEMU-KVM on the host did not validate all pointers provided from a guest system's QXL graphics card driver. A privileged guest user could use this flaw to cause the host to dereference an invalid pointer, causing the guest to crash (denial of service) or, possibly, resulting in the privileged guest user escalating their privileges on the host. (CVE-2010-0431)

A flaw was found in QEMU-KVM, allowing the guest some control over the index used to access the callback array during sub-page MMIO initialization. A privileged guest user could use this flaw to crash the guest (denial of service) or, possibly, escalate their privileges on the host. (CVE-2010-2784)

A NULL pointer dereference flaw was found when the host system had a processor with the Intel VT-x extension enabled. A privileged guest user could use this flaw to trick the host into emulating a certain instruction, which could crash the host (denial of service). (CVE-2010-0435)

This update also fixes the following bugs:

* running a "qemu-img" check on a faulty virtual machine image ended with a segmentation fault. With this update, the segmentation fault no longer occurs when running the "qemu-img" check. (BZ#610342)

* when attempting to transfer a file between two guests that were joined in the same virtual LAN (VLAN), the receiving guest unexpectedly quit. With this update, the transfer completes successfully. (BZ#610343)

* installation of a system was occasionally failing in KVM. This was caused by KVM using wrong permissions for large guest pages. With this update, the installation completes successfully. (BZ#616796)

* previously, the migration process would fail for a virtual machine because the virtual machine could not map all the memory. This was caused by a conflict that was initiated when a virtual machine was initially run and then migrated right away. With this update, the conflict no longer occurs and the migration process no longer fails. (BZ#618205)

* using a thinly provisioned VirtIO disk on iSCSI storage and performing a "qemu-img" check during an "e_no_space" event returned cluster errors. With this update, the errors no longer appear. (BZ#618206)

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.

4. Solution:

Before applying this update, make sure all previously-released errata relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to use the Red Hat Network to apply this update are available at http://kbase.redhat.com/faq/docs/DOC-11259

The following procedure must be performed before this update will take effect:

1) Stop all KVM guest virtual machines.

2) Either reboot the hypervisor machine or, as the root user, remove (using "modprobe -r [module]") and reload (using "modprobe [module]") all of the following modules which are currently running (determined using "lsmod"): kvm, ksm, kvm-intel or kvm-amd.

3) Restart the KVM guest virtual machines.

5. Bugs fixed (http://bugzilla.redhat.com/):

568809 - CVE-2010-0431 qemu: Insufficient guest provided pointers validation 570528 - CVE-2010-0435 kvm: vmx null pointer dereference 610342 - [kvm] segmentation fault when running qemu-img check on faulty image 610343 - Virtio: Transfer file caused guest in same vlan abnormally quit 616796 - KVM uses wrong permissions for large guest pages 618205 - SPICE - race in KVM/Spice would cause migration to fail (slots are not registered properly?) 618206 - [kvm] qemu image check returns cluster errors when using virtIO block (thinly provisioned) during e_no_space events (along with EIO errors) 619411 - CVE-2010-2784 qemu: insufficient constraints checking in exec.c:subpage_register()