Bug 1877383 (CVE-2020-25598) - CVE-2020-25598 xen: missing unlock in XENMEM_acquire_resource error path (XSA-334)
Summary: CVE-2020-25598 xen: missing unlock in XENMEM_acquire_resource error path (XSA...
Alias: CVE-2020-25598
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
Depends On: 1881616
Blocks: 1877386
TreeView+ depends on / blocked
Reported: 2020-09-09 14:01 UTC by Guilherme de Almeida Suckevicz
Modified: 2021-02-16 19:17 UTC (History)
25 users (show)

Fixed In Version:
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A security flaw was found in Xen. This flaw allows a buggy or malicious HVM subdomain to cause an RCU reference to be leaked. This issue causes subsequent administration operations on the host to livelock, resulting in a denial of service (DoS). The highest threat from this vulnerability is to system availability.
Clone Of:
Last Closed: 2020-09-22 20:41:22 UTC

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Description Guilherme de Almeida Suckevicz 2020-09-09 14:01:03 UTC
The RCU (Read, Copy, Update) mechanism is a synchronisation primitive. A buggy error path in the XENMEM_acquire_resource exits without releasing an RCU reference, which is conceptually similar to forgetting to unlock a spinlock.

Comment 1 Guilherme de Almeida Suckevicz 2020-09-09 14:01:09 UTC

Name: the Xen project

Comment 2 Mauro Matteo Cascella 2020-09-15 16:38:53 UTC

This issue can generally only be exploited by x86 HVM guests, as these are the only type of VM which have a QEMU stubdomain. x86 PV and PVH domains, as well as ARM guests typically don't use a stubdomain. Additionally, VMs using PV stubdomains or with emulators running in dom0 cannot exploit the vulnerability.

Xen 4.14 and later versions are vulnerable to this flaw. Red Hat Enterprise Linux 5 is not affected, as it shipped an older version of Xen which did not include the buggy code path.

Comment 3 Mauro Matteo Cascella 2020-09-15 16:38:56 UTC

Reconfiguring x86 HVM guests to use a PV or no stubdomain will mitigate the vulnerability.

Comment 4 Mauro Matteo Cascella 2020-09-22 18:26:40 UTC
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1881616]

Comment 5 Product Security DevOps Team 2020-09-22 20:41:22 UTC
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):


Comment 6 Mauro Matteo Cascella 2020-09-23 07:35:38 UTC
External References:


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