Bug 1047273 – VUL-0: CVE-2017-10923: xen: Xen through 4.8.x does not validate a vCPU array index upon the sendingof an SGI, which allows guest OS users to cause a denial of service(hypervisor crash), aka XSA-225.

Bug 1047273 - (CVE-2017-10923) VUL-0: CVE-2017-10923: xen: Xen through 4.8.x does not validate a vCPU array index upon the sendingof an SGI, which allows guest OS users to cause a denial of service(hypervisor crash), aka XSA-225.

(CVE-2017-10923)
Summary:	VUL-0: CVE-2017-10923: xen: Xen through 4.8.x does not validate a vCPU array ...

Status:	RESOLVED UPSTREAM

Classification:	Novell Products
Product:	SUSE Security Incidents
Classification:	Novell Products
Component:	Incidents
Version:	unspecified
Hardware:	Other Other

Priority:	P5 - None Severity: Normal
Target Milestone:	---
Assigned To:	Charles Arnold
QA Contact:	Security Team bot

URL:	https://smash.suse.de/issue/187845/
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Reported:	2017-07-05 06:14 UTC by Marcus Meissner
Modified:	2017-07-05 06:14 UTC (History)
CC List:	1 user (show)

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Found By:	Security Response Team
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Description Marcus Meissner 2017-07-05 06:14:14 UTC

CVE-2017-10923

Xen through 4.8.x does not validate a vCPU array index upon the sending
of an SGI, which allows guest OS users to cause a denial of service
(hypervisor crash), aka XSA-225.

https://xenbits.xen.org/xsa/advisory-225.html


References:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2017-10923
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-10923

Comment 1 Marcus Meissner 2017-07-05 06:14:47 UTC

ARM only, we do not ship XEN on arm:


                    Xen Security Advisory XSA-225
                              version 2

           arm: vgic: Out-of-bound access when sending SGIs

UPDATES IN VERSION 2
====================

Public release.

ISSUE DESCRIPTION
=================

ARM guests can send SGI (i.e. IPI) targeting a list of vCPUs using the
MMIO register GICD_SGIR (GICv2) or System Register ICC_SGI1R (GICv3).
However, the emulation code does not sanitize the list and will
directly access an array without checking whether the array index is
within bounds.

IMPACT
======

A guest may cause a hypervisor crash, resulting in a Denial of Service
(DoS).

VULNERABLE SYSTEMS
==================

Xen versions 4.6 and onwards are affected.  Xen versions 4.5 and
earlier are not affected.

Only ARM systems are affected.  x86 systems are not affected.
                    Xen Security Advisory XSA-225
                              version 2

           arm: vgic: Out-of-bound access when sending SGIs

UPDATES IN VERSION 2
====================

Public release.

ISSUE DESCRIPTION
=================

ARM guests can send SGI (i.e. IPI) targeting a list of vCPUs using the
MMIO register GICD_SGIR (GICv2) or System Register ICC_SGI1R (GICv3).
However, the emulation code does not sanitize the list and will
directly access an array without checking whether the array index is
within bounds.

IMPACT
======

A guest may cause a hypervisor crash, resulting in a Denial of Service
(DoS).

VULNERABLE SYSTEMS
==================

Xen versions 4.6 and onwards are affected.  Xen versions 4.5 and
earlier are not affected.

Only ARM systems are affected.  x86 systems are not affected.

MITIGATION
==========

On systems where the guest kernel is controlled by the host rather than
guest administrator, running only kernels which only send sane IPIs
(i.e. targeting valid CPUs) will prevent untrusted guest users from
exploiting this issue.  However untrusted guest administrators can
still trigger it unless further steps are taken to prevent them from
loading code into the kernel (e.g by disabling loadable modules etc) or
from using other mechanisms which allow them to run code at kernel
privilege.

CREDITS
=======

This issue was discovered by Julien Grall of ARM.

MITIGATION
==========

On systems where the guest kernel is controlled by the host rather than
guest administrator, running only kernels which only send sane IPIs
(i.e. targeting valid CPUs) will prevent untrusted guest users from
exploiting this issue.  However untrusted guest administrators can
still trigger it unless further steps are taken to prevent them from
loading code into the kernel (e.g by disabling loadable modules etc) or
from using other mechanisms which allow them to run code at kernel
privilege.

CREDITS
=======

This issue was discovered by Julien Grall of ARM.