Bug 1877366 (CVE-2020-25603) - CVE-2020-25603 xen: missing memory barriers when accessing/allocating an event channel (XSA-340)
Summary: CVE-2020-25603 xen: missing memory barriers when accessing/allocating an even...
Keywords:
Status: CLOSED WONTFIX
Alias: CVE-2020-25603
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1881583
Blocks: 1877386
TreeView+ depends on / blocked
 
Reported: 2020-09-09 13:12 UTC by Guilherme de Almeida Suckevicz
Modified: 2021-02-16 19:17 UTC (History)
25 users (show)

Fixed In Version:
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Doc Text:
A security flaw was found in Xen. Event channels control structures can be accessed without lock as long as the port is considered to be valid. A malicious guest may be able to cause a hypervisor crash resulting in a denial of service (DoS). An information leak and privilege escalation cannot be excluded. The highest threat from this vulnerability is to system availability.
Clone Of:
Environment:
Last Closed: 2020-09-22 20:41:04 UTC
Embargoed:

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Description Guilherme de Almeida Suckevicz 2020-09-09 13:12:53 UTC 
Event channels control structures can be accessed lockless as long as the port is considered to be valid. Such sequence is missing appropriate memory barrier (e.g smp_*mb()) to prevent both the compiler and CPU to re-order access.
Comment 1 Guilherme de Almeida Suckevicz 2020-09-09 13:20:43 UTC 
Acknowledgments:

Name: the Xen project
Comment 2 Mauro Matteo Cascella 2020-09-15 08:22:29 UTC 
Mitigation:

There is no known mitigation for this flaw apart from applying the patch.
Comment 4 Mauro Matteo Cascella 2020-09-15 10:19:56 UTC 
Statement:

Systems running all versions of Xen are affected by this flaw. Whether a system is vulnerable will depend on the CPU and compiler used to build Xen. For all the systems, the presence and the scope of the vulnerability depends on the precise re-ordering performed by the compiler used to build Xen. x86 systems are only vulnerable if a compiler performs re-ordering. Arm systems will also be vulnerable if the CPU is able to re-order memory access.

This flaw has been rated as having a security impact of Moderate, and is not currently planned to be addressed in future updates of Red Hat Enterprise Linux 5. Red Hat Enterprise Linux 5 is now in Extended Life Phase of the support and maintenance life cycle. For additional information, refer to the Red Hat Enterprise Linux Life Cycle: https://access.redhat.com/support/policy/updates/errata/.
Comment 5 Mauro Matteo Cascella 2020-09-22 17:52:30 UTC 
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1881583]
Comment 6 Product Security DevOps Team 2020-09-22 20:41:04 UTC 
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2020-25603
Comment 7 Mauro Matteo Cascella 2020-09-23 07:32:46 UTC 
External References:

https://xenbits.xen.org/xsa/advisory-340.html
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