xen - several vulnerabilities

Several vulnerabilities were discovered in the Xen virtual machine
hypervisor.

• CVE-2011-1166
  A 64-bit guest can get one of its vCPUs into non-kernel
  mode without first providing a valid non-kernel pagetable,
  thereby locking up the host system.
• CVE-2011-1583, CVE-2011-3262
  Local users can cause a denial of service and possibly execute
  arbitrary code via a crafted paravirtualised guest kernel image.
• CVE-2011-1898
  When using PCI passthrough on Intel VT-d chipsets that do not
  have interrupt remapping, guest OS users can gain host OS
  privileges by writing to the interrupt injection registers.

The oldstable distribution (lenny) contains a different version of Xen
not affected by these problems.

For the stable distribution (squeeze), this problem has been fixed in
version 4.0.1-4.

For the testing (wheezy) and unstable distribution (sid), this problem
has been fixed in version 4.1.1-1.

We recommend that you upgrade your xen packages.