arch/x86/entry/entry_64.S in the Linux kernel before 4.1.6 on the x86_64 platform does not properly determine when nested NMI processing is occurring, which allows local users to cause a denial of service (skipped NMI) by modifying the rsp register, issuing a syscall instruction, and triggering an NMI. http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-3291
