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Bug 624122 (CVE-2017-10917) - <app-emulation/xen-4.7.3: NULL pointer deref in event channel poll
Summary: <app-emulation/xen-4.7.3: NULL pointer deref in event channel poll
Alias: CVE-2017-10917
Product: Gentoo Security
Classification: Unclassified
Component: Vulnerabilities (show other bugs)
Hardware: All Linux
: Normal minor (vote)
Assignee: Gentoo Security
Whiteboard: B3 [noglsa cve]
Depends on: CVE-2017-10920, CVE-2017-10921, CVE-2017-10922
  Show dependency tree
Reported: 2017-07-07 14:58 UTC by Christopher Díaz Riveros (RETIRED)
Modified: 2017-10-15 20:10 UTC (History)
1 user (show)

See Also:
Package list:
Runtime testing required: ---


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Description Christopher Díaz Riveros (RETIRED) gentoo-dev Security 2017-07-07 14:58:00 UTC
From $URL:


When polling event channels, in general arbitrary port numbers can be
specified.  Specifically, there is no requirement that a polled event
channel ports has ever been created.  When the code was generalised
from an earlier implementation, introducing some intermediate
pointers, a check should have been made that these intermediate
pointers are non-NULL.  However, that check was omitted.


A malicious or buggy guest may cause the hypervisor to access
addresses it doesn't control, usually leading to a host crash (Denial
of Service).  Information leaks cannot be excluded.


Xen versions 4.4 and newer are vulnerable.  Xen versions 4.3 and
earlier are not affected.

Both x86 and ARM systems are vulnerable.

While all guest kinds can cause a Denial of Service, only x86 PV guests
may be able to leverage the possible information leaks.


There is no known mitigation.


This issue was discovered by Ankur Arora of Oracle.


Applying the appropriate attached patch resolves this issue.

xsa221.patch           Xen 4.4.x and later, including xen-unstable

$ sha256sum xsa221*
2425396a713466808b0f75f91337be4dd20a4dee7733972b04489773c6e97655  xsa221.patch


Deployment of the patches and/or mitigations described above (or
others which are substantially similar) is permitted during the
embargo, even on public-facing systems with untrusted guest users and

But: Distribution of updated software is prohibited (except to other
members of the predisclosure list).

Predisclosure list members who wish to deploy significantly different
patches and/or mitigations, please contact the Xen Project Security

(Note: this during-embargo deployment notice is retained in
post-embargo publicly released Xen Project advisories, even though it
is then no longer applicable.  This is to enable the community to have
oversight of the Xen Project Security Team's decisionmaking.)
Comment 1 Yixun Lan archtester gentoo-dev 2017-07-12 07:32:25 UTC
commit 7a8fc554850ee501e1ad705b4154874adf102947 
Author: Yixun Lan <>             
Date:   Wed Jul 12 15:15:52 2017 +0800          

    app-emulation/xen: security bump            
    fix XSA-217,218,219,220,221,222,223,224,225 
    Gentoo-Bug: 624112,624114,624116,624118,624120,624122,624124,624126,624130                  
    Package-Manager: Portage-2.3.6, Repoman-2.3.2                                               

:100644 100644 6534404116c... 49df2654a33... M  app-emulation/xen/Manifest                      
:000000 100644 00000000000... f66bd1b70f8... A  app-emulation/xen/xen-4.7.3.ebuild              
:000000 100644 00000000000... bf73951bc39... A  app-emulation/xen/xen-4.8.1-r2.ebuild
Comment 2 Christopher Díaz Riveros (RETIRED) gentoo-dev Security 2017-07-21 04:22:09 UTC
Thank you Yixun Lan

Arches please let us know when all is stable
Comment 3 Yury German Gentoo Infrastructure gentoo-dev 2017-08-20 21:56:48 UTC
Added to an existing GLSA Request.

Maintainer(s), please drop the vulnerable version(s).
Comment 4 Aaron Bauman (RETIRED) gentoo-dev 2017-10-15 20:10:51 UTC
GLSA Vote: No

Cleanup will occur in another bug.