xen - denial of service

Multiple denial of service vulnerabilities have been discovered
in the Xen Hypervisor. One of the issue
(CVE-2012-5513)
could even lead to privilege escalation from guest to host.

Some of the recently published Xen Security Advisories
(XSA 25
and 28)
are not fixed by this update and should be fixed in a future release.

• CVE-2011-3131
  (XSA 5):
  DoS using I/OMMU faults from PCI-passthrough guest
  A VM that controls a PCI[E] device directly can cause it to issue DMA
  requests to invalid addresses. Although these requests are denied by the
  I/OMMU, the hypervisor needs to handle the interrupt and clear the error from
  the I/OMMU, and this can be used to live-lock a CPU and potentially hang the
  host.
• CVE-2012-4535
  (XSA 20):
  Timer overflow DoS vulnerability
  A guest which sets a VCPU with an inappropriate deadline can cause an
  infinite loop in Xen, blocking the affected physical CPU indefinitely.
• CVE-2012-4537
  (XSA 22):
  Memory mapping failure DoS vulnerability
  When set_p2m_entry fails, Xen’s internal data structures (the p2m and m2p
  tables) can get out of sync. This failure can be triggered by unusual guest
  behaviour exhausting the memory reserved for the p2m table. If it happens,
  subsequent guest-invoked memory operations can cause Xen to fail an assertion
  and crash.
• CVE-2012-4538
  (XSA 23):
  Unhooking empty PAE entries DoS vulnerability
  The HVMOP_pagetable_dying hypercall does not correctly check the
  caller’s pagetable state, leading to a hypervisor crash.
• CVE-2012-4539
  (XSA 24):
  Grant table hypercall infinite loop DoS vulnerability
  Due to inappropriate duplicate use of the same loop control variable,
  passing bad arguments to GNTTABOP_get_status_frames can cause an
  infinite loop in the compat hypercall handler.
• CVE-2012-5510
  (XSA 26):
  Grant table version switch list corruption vulnerability
  Downgrading the grant table version of a guest involves freeing its status
  pages. This freeing was incomplete - the page(s) are freed back to the
  allocator, but not removed from the domain’s tracking list. This would cause
  list corruption, eventually leading to a hypervisor crash.
• CVE-2012-5513
  (XSA 29):
  XENMEM_exchange may overwrite hypervisor memory
  The handler for XENMEM_exchange accesses guest memory without range checking
  the guest provided addresses, thus allowing these accesses to include the
  hypervisor reserved range.

A malicious guest administrator can cause Xen to crash. If the out of address
space bounds access does not lead to a crash, a carefully crafted privilege
escalation cannot be excluded, even though the guest doesn’t itself control
the values written.

• CVE-2012-5514
  (XSA 30):
  Broken error handling in guest_physmap_mark_populate_on_demand()
  guest_physmap_mark_populate_on_demand(), before carrying out its actual
  operation, checks that the subject GFNs are not in use. If that check fails,
  the code prints a message and bypasses the gfn_unlock() matching the
  gfn_lock() carried out before entering the loop.
  A malicious guest administrator can then use it to cause Xen to hang.
• CVE-2012-5515
  (XSA 31):
  Several memory hypercall operations allow invalid extent order values
  Allowing arbitrary extent_order input values for XENMEM_decrease_reservation,
  XENMEM_populate_physmap, and XENMEM_exchange can cause arbitrarily long time
  being spent in loops without allowing vital other code to get a chance to
  execute. This may also cause inconsistent state resulting at the completion
  of these hypercalls.

For the stable distribution (squeeze), these problems have been fixed in
version 4.0.1-5.5.

For the testing distribution (wheezy), these problems have been fixed in
version 4.1.3-6.

For the unstable distribution (sid), these problems have been fixed in
version 4.1.3-6.

We recommend that you upgrade your xen packages.