Bug 1271621 (CVE-2015-7812, xsa145) - CVE-2015-7812 xen: Host crash when preempting a multicall on ARM
Summary: CVE-2015-7812 xen: Host crash when preempting a multicall on ARM
Keywords:
Status: CLOSED NOTABUG
Alias: CVE-2015-7812, xsa145
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1276344
Blocks: 1271637
TreeView+ depends on / blocked
 
Reported: 2015-10-14 11:59 UTC by Adam Mariš
Modified: 2021-02-17 04:51 UTC (History)
10 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2018-03-07 09:49:44 UTC
Embargoed:


Attachments (Terms of Use)
Upstream patch (1.60 KB, patch)
2015-10-14 12:01 UTC, Adam Mariš
no flags Details | Diff

Description Adam Mariš 2015-10-14 11:59:22 UTC
A vulnerability allowing malicious geust to crash the host was found. Early versions of Xen on ARM did not support "multicall" functionality (the ability to perform multiple operations via a single hypercall) and therefore stubbed out the functionality needed to support preemption of multicalls in a manner which crashed the host. When multicall support was subsequently added these stubs were not replaced with the correct functionality and therefore exposed to guests a code path which crashes the host. Any guest can issue a preemptable hypercall via the multicall interface to exploit this vulnerability. Both 32- and 64-bit ARM systems are vulnerable from Xen 4.4 onward.

Mitigation:

On systems where the guest kernel is controlled by the host rather than guest administrator, running only kernels which do not make use of multicall functionality 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.

Comment 1 Adam Mariš 2015-10-14 12:01:08 UTC
Created attachment 1082800 [details]
Upstream patch

Comment 2 Martin Prpič 2015-10-29 13:40:19 UTC
External References:

http://xenbits.xen.org/xsa/advisory-145.html

Comment 3 Martin Prpič 2015-10-29 13:51:28 UTC
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1276344]

Comment 4 Fedora Update System 2015-11-08 22:21:00 UTC
xen-4.5.1-14.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.

Comment 5 Fedora Update System 2015-11-10 00:22:13 UTC
xen-4.5.1-14.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.

Comment 6 Fedora Update System 2015-11-10 00:50:22 UTC
xen-4.4.3-7.fc21 has been pushed to the Fedora 21 stable repository. If problems still persist, please make note of it in this bug report.


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