KVM: VMX: fix use after free of vmx->loaded_vmcs

[Marcelo Tosatti <mtosatti@redhat.com>]

After free_loaded_vmcs executes, the "loaded_vmcs" structure 
is kfreed, and now vmx->loaded_vmcs points to a kfreed area. 
Subsequent free_loaded_vmcs then attempts to manipulate 
vmx->loaded_vmcs.

Switch the order to avoid the problem.

https://bugzilla.redhat.com/show_bug.cgi?id=1047892

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index da7837e..2efa33f0 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7332,8 +7332,8 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
 	free_vpid(vmx);
-	free_nested(vmx);
 	free_loaded_vmcs(vmx->loaded_vmcs);
+	free_nested(vmx);
 	kfree(vmx->guest_msrs);
 	kvm_vcpu_uninit(vcpu);
 	kmem_cache_free(kvm_vcpu_cache, vmx);