Download Xen 4.2.2

Xen is a “virtual machine hypervisor” for the x86 platform, allowing multiple operating systems to run simultaneously on a single system without drastically impacting performance. For more information about Xen and its community, please refer to this one and this one pages. Currently only Linux and NetBSD are supported as host systems, but work is underway to fully support other operating systems as well. The developers released Xen 4.2.2 a few days ago with the following changes:

Version 4.2.2

Xen 4.2.2 is a maintenance release in the 4.2 series and contains: We recommend that all users of Xen 4.2.1 upgrade to Xen 4.2.2.

This release fixes the following critical vulnerabilities:

• CVE-2012-5634 / XSA-33: VT-d interrupt remapping source validation flaw
• CVE-2013-0151 / XSA-34: nested virtualization on 32-bit exposes host crash
• CVE-2013-0152 / XSA-35: Nested HVM exposes host to being driven out of memory by guest
• CVE-2013-0153 / XSA-36: interrupt remap entries shared and old ones not cleared on AMD IOMMUs
• CVE-2013-0154 / XSA-37: Hypervisor crash due to incorrect ASSERT (debug build only)
• CVE-2013-0215 ​​/ XSA-38: oxenstored incorrect handling of certain Xenbus ring states
• CVE-2012-6075 / XSA-41: qemu (e1000 device driver): Buffer overflow when processing large packets
• CVE-2013-1917 / XSA-44: Xen PV DoS vulnerability with SYSENTER
• CVE-2013-1919 / XSA-46: Several access permission issues with IRQs for unprivileged guests
• CVE-2013-1920 / XSA-47: Potential use of freed memory in event channel operations
• CVE-2013-1922 / XSA-48: qemu-nbd format-guessing due to missing format specification

This release contains many bug fixes and improvements (around 100 since Xen 4.2.1). The highlights are:

• ACPI APEI/ERST finally working on production systems
• Bug fixes for other low level system state handling
• Bug fixes and improvements to the libxl tool stack
• Bug fixes to nested virtualization

Version 4.2.1

Xen 4.2.1 is a maintenance release in the 4.2 series and contains: We recommend that all users of Xen 4.2.0 upgrade to Xen 4.2.1.
The release fixes the following critical vulnerabilities:

• CVE-2012-4535 / XSA-20: Timer overflow DoS vulnerability
• CVE-2012-4537 / XSA-22: Memory mapping failure DoS vulnerability
• CVE-2012-4538 / XSA-23: Unhooking empty PAE entries DoS vulnerability
• CVE-2012-4539 / XSA-24: Grant table hypercall infinite loop DoS vulnerability
• CVE-2012-4544, CVE-2012-2625 / XSA-25: Xen domain builder Out-of-memory due to malicious kernel/ramdisk
• CVE-2012-5510 / XSA-26: Grant table version switch list corruption vulnerability
• CVE-2012-5511 / XSA-27: Several HVM operations do not validate the range of their inputs
• CVE-2012-5513 / XSA-29: XENMEM_exchange may overwrite hypervisor memory
• CVE-2012-5514 / XSA-30: Broken error handling in guest_physmap_mark_populate_on_demand()
• CVE-2012-5515 / XSA-31: Several memory hypercall operations allow invalid extent order values
• CVE-2012-5525 / XSA-32: several hypercalls do not validate input GFNs

Among many bug fixes and improvements (around 100 since Xen 4.2.0):

• A fix for a long standing time management issue
• Bug fixes for S3 (suspend to RAM) handling
• Bug fixes for other low level system state handling
• Bug fixes and improvements to the libxl tool stack
• Bug fixes to nested virtualization

Version 4.2.0

The Xen 4.2 release contains a number of important new features and updates including:

The release incorporates many new features and improvements to existing features. There are improvements across the board including to Security, Scalability, Performance and Documentation.

• XL is now the default toolstack: Significant effort has gone in to the XL tool toolstack in this release and it is now feature complete and robust enough that we have made it the default. This toolstack can now replace xend in the majority of deployments, see XL vs Xend Feature Comparison. As well as improving XL the underlying libxl library has been significantly improved and supports the majority of the most common toolstack features. In addition the API has been declared stable which should make it even easier for external toolstack such as libvirt and XCP’s xapi to make full use of this functionality in the future.
• Large Systems: Following on from the improvements made in 4.1 Xen now supports even larger systems, with up to 4095 host CPUs and up to 512 guest CPUs. In addition toolstack feature like the ability to automatically create a CPUPOOL per NUMA node and more intelligent placement of guest VCPUs on NUMA nodes have further improved the Xen experience on large systems. Other new features, such as multiple PCI segment support have also made a positive impact on such systems.
• Improved security: The XSM/Flask subsystem has seen several enhancements, including improved support for disaggregated systems and a rewritten example policy which is clearer and simpler to modify to suit local requirements.
• Documentation: The Xen documentation has been much improved, both the in-tree documentation and the wiki. This is in no small part down to the success of the Xen Document Days so thanks to all who have taken part.

You can find more information in the Xen 4.2 release notes, the Xen 4.2 feature list and the Also see the Xen 4.x Feature Matrix.

Xen Hypervisor 4.2 Acknowledgments
Contributions were made to this release by 124 individuals from 43 organizations, not counting contributions to external projects such as the BSDs, Linux or qemu. Many thanks to everyone who contributed to this release, either through code, testing, documentation or in any other way.

The diagram below shows organizations which contributed more than 1% in lines of code to the Xen 4.2 release. Several items in the diagram discribe groups of people or organisations: Individual covers contributions by individuals whose affiliation is unknown, Misc covers contributions by commercial organizations which did not go above 1% individually and University covers contributions by Universities which did not go above 1% individually .

For a complete breakdown of community contributions, see Xen 4.2 Acknowledgments.