Information

Advisory

XSA-358

Public release

2020-12-15 12:00

Updated

2020-12-16 17:04

Version

5

CVE(s)

CVE-2020-29570

Title

FIFO event channels control block related ordering

Filesadvisory-358.txt (signed advisory file)
xsa358.meta
xsa358.patch
xsa358-4.14.patchAdvisory

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256

        Xen Security Advisory CVE-2020-29570 / XSA-358
                           version 5

      FIFO event channels control block related ordering

UPDATES IN VERSION 5

“Unstable” patch updated (needed re-basing).

ISSUE DESCRIPTION

Recording of the per-vCPU control block mapping maintained by Xen and that of pointers into the control block is reversed. The consumer assumes, seeing the former initialized, that the latter are also ready for use.

IMPACT

Malicious or buggy guest kernels can mount a Denial of Service (DoS) attack affecting the entire system.

VULNERABLE SYSTEMS

All Xen versions from 4.4 onwards are vulnerable. Xen versions 4.3 and earlier are not vulnerable.

MITIGATION

There is no known mitigation.

CREDITS

This issue was discovered by Julien Grall of Amazon.

RESOLUTION

Applying the appropriate attached patch resolves this issue.

Note that patches for released versions are generally prepared to apply to the stable branches, and may not apply cleanly to the most recent release tarball. Downstreams are encouraged to update to the tip of the stable branch before applying these patches.

xsa358.patch xen-unstable xsa358-4.14.patch Xen 4.14 - 4.10

$ sha256sum xsa358* 0e8428a52e9bedafb2d8cbbb8dffae4e882e4b0898e4e7df3576c99e0e607167 xsa358.meta c0763c85287d138a02dc795aa5d2e903ca7efc641390bee53ea2f7473f4f95af xsa358.patch 937a3786d3d0147aef63eed373ed1df9ede75d1fabf5ad8f6ccaacfbf7fbcf42 xsa358-4.14.patch $

DEPLOYMENT DURING EMBARGO

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 administrators.

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 Team.

(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deployment notice is retained in post-embargo publicly released Xen Project advisories, even though it is then no longer applicable.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.)

For more information about permissible uses of embargoed information, consult the Xen Project community’s agreed Security Policy: http://www.xenproject.org/security-policy.html -----BEGIN PGP SIGNATURE-----

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Xenproject.org Security Team