CVE-2026-72287

Descrição

In the Linux kernel, the following vulnerability has been resolved: KVM: nVMX: Move vTPR vs. TPR Threshold consistency check into -normal- checks Move the off-by-default consistency check for vmcs12.tpr_threshold vs. the virtual APIC vTPR into the -normal- controls checks, as waiting until KVM has loaded some amount of state is unnecessary and actively dangerous. Specifically, failure to unwind vmcs01.GUEST_CR3 to KVM-s value when EPT is disabled results in KVM running L1 with an L1-controlled CR3, not with KVM-s CR3! Alternatively, KVM could simply reset the MMU to force a reload of vmcs01.GUEST_CR3, but the _only_ reason the check was shoved into a -late- flow was to wait until the vmcs12 pages were retrieved. Rather than build up more crusty code, simply access vTPR using a regular guest memory access (performance isn-t a concern). To circumvent the restrictions that led to KVM deferring nested_get_vmcs12_pages(), (a) use a VM-scoped API to read guest memory so that it always hits non-SMM memslots (for RSM), and (b) skip the check (since its off-by-default anyways) when the vCPU doesn-t want to run, i.e. when userspace is restoring/stuffing state. If reading guest memory fails, simply skip the consistency check, as KVM-s de facto ABI is that VMX instruction accesses to non-existent memory get PCI Bus Error semantics, where reads return 0xFFs. And if vTPR=0xFF, then the vTPR is guaranteed to be greater than or equal to TPR_THRESHOLD.