SuSE 11.1 Security Update : Xen (SAT Patch Number 6399)
High Nessus Plugin ID 64233
SynopsisThe remote SuSE 11 host is missing one or more security updates.
DescriptionThree security issues were found in XEN.
Two security issues are fixed by this update :
- Due to incorrect fault handling in the XEN hypervisor it was possible for a XEN guest domain administrator to execute code in the XEN host environment.
- Also a guest user could crash the guest XEN kernel due to a protection fault bounce. The third fix is changing the Xen behaviour on certain hardware:. (CVE-2012-0218)
- The issue is a denial of service issue on older pre-SVM AMD CPUs (AMD Erratum 121). AMD Erratum #121 is described in 'Revision Guide for AMD Athlon 64 and AMD Opteron Processors':
The following 130nm and 90nm (DDR1-only) AMD processors are subject to this erratum :
- First-generation AMD-Opteron(tm) single and dual core processors in either 939 or 940 packages :
- AMD Opteron(tm) 100-Series Processors
- AMD Opteron(tm) 200-Series Processors
- AMD Opteron(tm) 800-Series Processors
- AMD Athlon(tm) processors in either 754, 939 or 940 packages
- AMD Sempron(tm) processor in either 754 or 939 packages
- AMD Turion(tm) Mobile Technology in 754 package This issue does not effect Intel processors.
The impact of this flaw is that a malicious PV guest user can halt the host system.
As this is a hardware flaw, it is not fixable except by upgrading your hardware to a newer revision, or not allowing untrusted 64bit guestsystems.
The patch changes the behaviour of the host system booting, which makes it unable to create guest machines until a specific boot option is set.
There is a new XEN boot option 'allow_unsafe' for GRUB which allows the host to start guests again.
This is added to /boot/grub/menu.lst in the line looking like this :
kernel /boot/xen.gz .... allow_unsafe
Note: .... in this example represents the existing boot options for the host.
SolutionApply SAT patch number 6399.