XSA-121

CVE-2015-2044

问题描述

http://xenbits.xen.org/xsa/advisory-121.html

information leak via internal x86 system device emulation

Emulation routines in the hypervisor dealing with certain system devices check whether the access size by the guest is a supported one. When the access size is unsupported these routines failed to set the data to be returned to the guest for read accesses, so that hypervisor stack contents are copied into the destination of the operation, thus becoming visible to the guest.

uninitialized memory, hypervisor栈上的内容会被拷贝到虚拟机。

Patch描述

http://xenbits.xen.org/xsa/xsa121.patch

x86/HVM: return all ones on wrong-sized reads of system device I/O ports

So far the value presented to the guest remained uninitialized.

将所有device I/O的ports初始化成全1：*val = ~0;

Consequence

A malicious HVM guest might be able to read sensitive data relating to other guests.

information leak