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kvm: nVMX: Don't allow L2 to access the hardware CR8
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If L1 does not specify the "use TPR shadow" VM-execution control in
vmcs12, then L0 must specify the "CR8-load exiting" and "CR8-store
exiting" VM-execution controls in vmcs02. Failure to do so will give
the L2 VM unrestricted read/write access to the hardware CR8.

This fixes CVE-2017-12154.

Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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jsmattsonjr authored and bonzini committed Sep 15, 2017
1 parent 488e32f commit 51aa68e
Showing 1 changed file with 5 additions and 0 deletions.
5 changes: 5 additions & 0 deletions arch/x86/kvm/vmx.c
Original file line number Diff line number Diff line change
Expand Up @@ -10525,6 +10525,11 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
if (exec_control & CPU_BASED_TPR_SHADOW) {
vmcs_write64(VIRTUAL_APIC_PAGE_ADDR, -1ull);
vmcs_write32(TPR_THRESHOLD, vmcs12->tpr_threshold);
} else {
#ifdef CONFIG_X86_64
exec_control |= CPU_BASED_CR8_LOAD_EXITING |
CPU_BASED_CR8_STORE_EXITING;
#endif
}

/*
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