hugetlbfs use may crash PV Linux guests

2016-04-1412:00:00

Xen Project

xenbits.xen.org

CVSS2

2.1

Attack Vector

LOCAL

Attack Complexity

LOW

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

PARTIAL

AV:L/AC:L/Au:N/C:N/I:N/A:P

CVSS3

5.5

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

HIGH

CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS

0.001

Percentile

28.1%

JSON

ISSUE DESCRIPTION

Huge (2Mb) pages are generally unavailable to PV guests. Since x86 Linux pvops-based kernels are generally multi purpose, they would normally be built with hugetlbfs support enabled. Use of that functionality by an application in a PV guest would cause an infinite page fault loop, and an OOPS to occur upon an attempt to terminate the hung application.

IMPACT

Depending on the guest kernel configuration, the OOPS could result in a kernel crash (guest DoS).

VULNERABLE SYSTEMS

All upstream x86 Linux versions operating as PV Xen guests are vulnerable.
ARM systems are not vulnerable. x86 HVM guests are not vulnerable.
x86 Linux versions derived from linux-2.6.18-xen.hg (XenoLinux) are not vulnerable.
Oracle Unbreakable Enterprise Kernels are not vulnerable.
We believe that non-Linux guests are not vulnerable, as we are not aware of any with an analogous bug.