A PV guest could DoS Xen while unmapping a grant To address XSA-380, reference counting was introduced for grant mappings for the case where a PV guest would have the IOMMU enabled. PV guests can request two forms of mappings. When both are in use for any individual mapping, unmapping of such a mapping can be requested in two steps. The reference count for such a mapping would then mistakenly be decremented twice. Underflow of the counters gets detected, resulting in the triggering of a hypervisor bug check.
The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Xen | Xen | 3.2.0 (including) | 4.13.0 (excluding) |
| Xen | Ubuntu | bionic | * |
| Xen | Ubuntu | impish | * |
| Xen | Ubuntu | kinetic | * |
| Xen | Ubuntu | lunar | * |
| Xen | Ubuntu | mantic | * |
| Xen | Ubuntu | trusty | * |
| Xen | Ubuntu | xenial | * |