Description
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.
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Remediation
No vendor fix or workaround currently provided.
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Tracking
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Advisories
| Source | ID | Title |
|---|---|---|
Debian DSA |
DSA-4723-1 | xen security update |
EUVD |
EUVD-2020-4081 | 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. |
Ubuntu USN |
USN-5617-1 | Xen vulnerabilities |
References
History
No history.
Status: PUBLISHED
Assigner: mitre
Published:
Updated: 2024-08-04T11:41:59.001Z
Reserved: 2020-04-14T00:00:00.000Z
Link: CVE-2020-11739
No data.
Status : Modified
Published: 2020-04-14T13:15:12.703
Modified: 2024-11-21T04:58:31.313
Link: CVE-2020-11739
OpenCVE Enrichment
No data.
Weaknesses
Debian DSA
EUVD
Ubuntu USN