description: x86 pv: Race condition in typeref acquisition Xen maintains a type reference count for pages, in addition to a regular reference count. This scheme is used to maintain invariants required for Xen's safety, e.g. PV guests may not have direct writeable access to pagetables; updates need auditing by Xen. Unfortunately, the logic for acquiring a type reference has a race condition, whereby a safely TLB flush is issued too early and creates a window where the guest can re-establish the read/write mapping before writeability is prohibited.
problem types: unknown
affected:
{
product: xen
vendor: Xen
versions:
status: unknown, version: consult Xen advisory XSA-401
}
metrics:
other: [
content: {'description': {'description_data': [{'lang': 'eng', 'value': 'Malicious x86 PV guest administrators may be able to escalate privilege\nso as to control the whole system.'}]}}
type: unknown
]