CVE-2016-3158

The xrstor function in arch/x86/xstate.c in Xen 4.x does not properly
handle writes to the hardware FSW.ES bit when running on AMD64 processors,
which allows local guest OS users to obtain sensitive register content
information from another guest by leveraging pending exception and mask
bits. NOTE: this vulnerability exists because of an incorrect fix for
CVE-2013-2076.

Bugs

• <https://bugs.launchpad.net/ubuntu/+source/xen/+bug/1564772&gt;
• <https://bugs.launchpad.net/ubuntu/+source/xen/+bug/1581419&gt;