arch/x86/kvm/vmx.c in the KVM subsystem in the Linux kernel before 3.17.2 on Intel processors does not ensure that the value in the CR4 control register remains the same after a VM entry, which allows host OS users to kill arbitrary processes or cause a denial of service (system disruption) by leveraging /dev/kvm access, as demonstrated by PR_SET_TSC prctl calls within a modified copy of QEMU.
https://github.com/torvalds/linux/commit/d974baa398f34393db76be45f7d4d04fbdbb4a0a
https://bugzilla.redhat.com/show_bug.cgi?id=1153322
http://www.ubuntu.com/usn/USN-2421-1
http://www.ubuntu.com/usn/USN-2420-1
http://www.ubuntu.com/usn/USN-2419-1
http://www.ubuntu.com/usn/USN-2418-1
http://www.ubuntu.com/usn/USN-2417-1
http://www.securityfocus.com/bid/70691
http://www.openwall.com/lists/oss-security/2014/10/29/7
http://www.openwall.com/lists/oss-security/2014/10/21/4
http://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.17.2
http://www.debian.org/security/2014/dsa-3060
http://rhn.redhat.com/errata/RHSA-2015-0864.html
http://rhn.redhat.com/errata/RHSA-2015-0782.html
http://rhn.redhat.com/errata/RHSA-2015-0290.html
http://lists.opensuse.org/opensuse-security-announce/2015-04/msg00015.html
http://lists.opensuse.org/opensuse-security-announce/2015-03/msg00025.html
http://lists.opensuse.org/opensuse-security-announce/2015-03/msg00010.html
http://lists.opensuse.org/opensuse-security-announce/2015-01/msg00035.html