An issue was discovered in Xen through 4.13.x, allowing guest OS users to cause a denial of service or possibly gain privileges because of missing memory barriers in read-write unlock paths. The read-write unlock paths don't contain a memory barrier. On Arm, this means a processor is allowed to re-order the memory access with the preceding ones. In other words, the unlock may be seen by another processor before all the memory accesses within the "critical" section. As a consequence, it may be possible to have a writer executing a critical section at the same time as readers or another writer. In other words, many of the assumptions (e.g., a variable cannot be modified after a check) in the critical sections are not safe anymore. The read-write locks are used in hypercalls (such as grant-table ones), so a malicious guest could exploit the race. For instance, there is a small window where Xen can leak memory if XENMAPSPACE_grant_table is used concurrently. A malicious guest may be able to leak memory, or cause a hypervisor crash resulting in a Denial of Service (DoS). Information leak and privilege escalation cannot be excluded.
History

No history.

cve-icon MITRE

Status: PUBLISHED

Assigner: mitre

Published: 2020-04-14T12:17:49

Updated: 2024-08-04T11:41:59.001Z

Reserved: 2020-04-14T00:00:00

Link: CVE-2020-11739

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Modified

Published: 2020-04-14T13:15:12.703

Modified: 2023-11-07T03:15:04.020

Link: CVE-2020-11739

cve-icon Redhat

Severity : Moderate

Publid Date: 2020-04-14T00:00:00Z

Links: CVE-2020-11739 - Bugzilla