CVE-2026-45987

In the Linux kernel, the following vulnerability has been resolved:

KVM: nSVM: Sync interrupt shadow to cached vmcb12 after VMRUN of L2

After VMRUN in guest mode, nestedsynccontrolfromvmcb02() syncs fields written by the CPU from vmcb02 to the cached vmcb12. This is because the cached vmcb12 is used as the authoritative copy of some of the controls, and is the payload when saving/restoring nested state.

intstate is also written by the CPU, specifically bit 0 (i.e. SVMINTERRUPTSHADOWMASK) for nested VMs, but it is not sync'd to cached vmcb12. This does not cause a problem if KVMSETNESTEDSTATE preceeds KVMSETVCPUEVENTS in the restore path, as an interrupt shadow would be correctly restored to vmcb02 (KVMSETVCPUEVENTS overwrites what KVMSETNESTEDSTATE restored in int_state).

However, if KVMSETVCPUEVENTS preceeds KVMSETNESTEDSTATE, an interrupt shadow would be restored into vmcb01 instead of vmcb02. This would mostly be benign for L1 (delays an interrupt), but not for L2. For L2, the vCPU could hang (e.g. if a wakeup interrupt is delivered before a HLT that should have been in an interrupt shadow).

Sync intstate to the cached vmcb12 in nestedsynccontrolfromvmcb02() to avoid this problem. With that, KVMSETNESTEDSTATE restores the correct interrupt shadow state, and if KVMSETVCPU_EVENTS follows it would overwrite it with the same value.