The (1) libxl_set_memory_target function in tools/libxl/libxl.c and (2) libxl__build_post function in tools/libxl/libxl_dom.c in Xen 3.4.x through 4.6.x do not properly calculate the balloon size when using the populate-on-demand (PoD) system, which allows local HVM guest users to cause a denial of service (guest crash) via unspecified vectors related to "heavy memory pressure."
The MITRE CVE dictionary describes this issue as:
Find out more about CVE-2015-7972 from the MITRE CVE dictionary dictionary and NIST NVD.
NOTE: The following CVSS v2 metrics and score provided are preliminary and subject to review.
| Base Score | 4.7 |
|---|---|
| Base Metrics | AV:L/AC:M/Au:N/C:N/I:N/A:C |
| Access Vector | Local |
| Access Complexity | Medium |
| Authentication | None |
| Confidentiality Impact | None |
| Integrity Impact | None |
| Availability Impact | Complete |
Find out more about Red Hat support for the Common Vulnerability Scoring System (CVSS).
| Platform | Package | State |
|---|---|---|
| Red Hat Enterprise Linux 5 | xen | Not affected |
Reducing the guest's memory target, after guest startup, can cause the
guest's ballon driver to eliminate the PoD discrepancy. If the guest
successfully balloons down, it will no longer be vulnerable.
Vulmon