KVM: nVMX: Don't emulate instructions in guest mode

commit 07721feee46b4b248402133228235318199b05ec upstream.

[ Fixes: CVE-2020-2732 ]

vmx_check_intercept is not yet fully implemented. To avoid emulating
instructions disallowed by the L1 hypervisor, refuse to emulate
instructions by default.

Cc: stable@vger.kernel.org
[Made commit, added commit msg - Oliver]
Signed-off-by: NOliver Upton <oupton@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NShile Zhang <shile.zhang@linux.alibaba.com>
Acked-by: NCaspar Zhang <caspar@linux.alibaba.com>

arch/x86/kvm/vmx.c

@@ -13694,7 +13694,7 @@ static int vmx_check_intercept(struct kvm_vcpu *vcpu,
 	}
 
 	/* TODO: check more intercepts... */
-	return X86EMUL_CONTINUE;
+	return X86EMUL_UNHANDLEABLE;
 }
 
 #ifdef CONFIG_X86_64