The vmx_set_msr function in arch/x86/kvm/vmx.c in the VMX implementation in the KVM subsystem in the Linux kernel before 2.6.29.1 on the i386 platform allows guest OS users to cause a denial of service (OOPS) by setting the EFER_LME (aka "Long mode enable") bit in the Extended Feature Enable Register (EFER) model-specific register, which is specific to the x86_64 platform.