xen - several

Several vulnerabilities were discovered in Xen, a hypervisor.

• CVE-2012-0217
  Xen does not properly handle uncanonical return addresses on
  Intel amd64 CPUs, allowing amd64 PV guests to elevate to
  hypervisor privileges. AMD processors, HVM and i386 guests
  are not affected.
• CVE-2012-0218
  Xen does not properly handle SYSCALL and SYSENTER instructions
  in PV guests, allowing unprivileged users inside a guest
  system to crash the guest system.
• CVE-2012-2934
  Xen does not detect old AMD CPUs affected by AMD Erratum #121.

For CVE-2012-2934,
Xen refuses to start domUs on affected systems
unless the allow_unsafe option is passed.

For the stable distribution (squeeze), these problems have been fixed
in version 4.0.1-5.2.

For the testing distribution (wheezy) and the unstable distribution
(sid), these problems have been fixed in version
4.1.3~rc1+hg-20120614.a9c0a89c08f2-1.

We recommend that you upgrade your xen packages.