Security update for xen (important)

This update for xen fixes several issues.

These security issues were fixed:

• blkif responses leaked backend stack data, which allowed unprivileged
  guest to obtain sensitive information from the host or other guests
  (XSA-216, bsc#1042863)
• Page transfer might have allowed PV guest to elevate privilege (XSA-217,
  bsc#1042882)
• Races in the grant table unmap code allowed for informations leaks and
  potentially privilege escalation (XSA-218, bsc#1042893)
• Insufficient reference counts during shadow emulation allowed a
  malicious pair of guest to elevate their privileges to the privileges
  that XEN runs under (XSA-219, bsc#1042915)
• Stale P2M mappings due to insufficient error checking allowed malicious
  guest to leak information or elevate privileges (XSA-222, bsc#1042931)
• Grant table operations mishandled reference counts allowing malicious
  guests to escape (XSA-224, bsc#1042938)
• CVE-2017-9330: USB OHCI Emulation in qemu allowed local guest OS users
  to cause a denial of service (infinite loop) by leveraging an incorrect
  return value (bsc#1042160)
• CVE-2017-8309: Memory leak in the audio/audio.c allowed remote attackers
  to cause a denial of service (memory consumption) by repeatedly starting
  and stopping audio capture (bsc#1037243)
• CVE-2017-8905: Xen a failsafe callback, which might have allowed PV
  guest OS users to execute arbitrary code on the host OS (XSA-215,
  bsc#1034845).
• CVE-2017-9503: The MegaRAID SAS 8708EM2 Host Bus Adapter emulation
  support was vulnerable to a null pointer dereference issue which allowed
  a privileged user inside guest to crash the Qemu process on the host
  resulting in DoS (bsc#1043297)
• CVE-2017-9374: Missing free of ‘s->ipacket’, causes a host memory leak,
  allowing for DoS (bsc#1043074)
• CVE-2017-8112: hw/scsi/vmw_pvscsi.c allowed local guest OS privileged
  users to cause a denial of service (infinite loop and CPU consumption)
  via the message ring page count (bsc#1036470)
• Missing NULL pointer check in event channel poll allows guests to DoS
  the host (XSA-221, bsc#1042924)

These non-security issues were fixed:

• bsc#1032148: Ensure that time doesn’t goes backwards during live
  migration of HVM domU
• bsc#1031460: Fixed DomU Live Migration
• bsc#1014136: Fixed kdump SLES12-SP2
• bsc#1026236: Equalized paravirtualized vs. fully virtualized migration
  speed