kernel: kvm: insufficient sysenter emulation when invoked from 16-bit code

It was found that the Linux kernel KVM subsystem's sysenter instruction emulation was not sufficient. An unprivileged guest user could use this flaw to escalate their privileges by tricking the hypervisor to emulate a SYSENTER instruction in 16-bit mode, if the guest OS did not initialize the...

UBUNTU-CVE-2015-0239

The emsysenter function in arch/x86/kvm/emulate.c in the Linux kernel before 3.18.5, when the guest OS lacks SYSENTER MSR initialization, allows guest OS users to gain guest OS privileges or cause a denial of service guest OS crash by triggering use of a 16-bit code segment for emulation of a...