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KVM: nVMX: WARN if subtly-impossible VMFUNC conditions occur

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WARN and inject #UD when emulating VMFUNC for L2 if the function is
out-of-bounds or if VMFUNC is not enabled in vmcs12.  Neither condition
should occur in practice, as the CPU is supposed to prioritize the #UD
over VM-Exit for out-of-bounds input and KVM is supposed to enable
VMFUNC in vmcs02 if and only if it's enabled in vmcs12, but neither of
those dependencies is obvious.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210609234235.1244004-15-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson
2021-06-09 16:42:34 -07:00
committed by Paolo Bonzini
parent c906066288
commit 546e8398bc
1 changed files with 10 additions and 0 deletions
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10
arch/x86/kvm/vmx/nested.c
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@@ -5552,6 +5552,16 @@ static int handle_vmfunc(struct kvm_vcpu *vcpu)
}
vmcs12 = get_vmcs12(vcpu);
/*
* #UD on out-of-bounds function has priority over VM-Exit, and VMFUNC
* is enabled in vmcs02 if and only if it's enabled in vmcs12.
*/
if (WARN_ON_ONCE((function > 63) || !nested_cpu_has_vmfunc(vmcs12))) {
kvm_queue_exception(vcpu, UD_VECTOR);
return 1;
}
if (!(vmcs12->vm_function_control & BIT_ULL(function)))
goto fail;