Xen Security Advisory 236 (CVE-2017-15597) - pin count / page reference race in grant table code
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Xen Security Advisory CVE-2017-15597 / XSA-236
pin count / page reference race in grant table code
UPDATES IN VERSION 3
We now once again think that only Xen 4.2 and newer are vulnerable.
Fix grammar typo.
Grant copying code made an implication that any grant pin would be
accompanied by a suitable page reference. Other portions of code,
however, did not match up with that assumption. When such a grant
copy operation is being done on a grant of a dying domain, the
assumption turns out wrong.
A malicious guest administrator can cause hypervisor memory
corruption, most likely resulting in host crash and a Denial of
Service. Privilege escalation and information leaks cannot be ruled
Xen versions from 4.2 onwards are vulnerable. Xen versions 4.1 and
earlier are not vulnerable.
Both x86 and ARM are vulnerable, and on x86 both PV and HVM guests can
trigger the vulnerability.
Running only guests without para-virtual drivers, and known not to
issue grant table operations can avoid the vulnerability.
This issue was discovered by Pawel Wieczorkiewicz of Amazon.
Applying the appropriate attached patch resolves this issue.
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
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is then no longer applicable.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.)