KVM: nSVM: Avoid freeing uninitialized pointers in svm_set_nested_state()

The save and ctl pointers are passed uninitialized to kfree() when
svm_set_nested_state() follows the 'goto out_set_gif' path. While the
issue could've been fixed by initializing these on-stack varialbles to
NULL, it seems preferable to eliminate 'out_set_gif' label completely as
it is not actually a failure path and duplicating a single svm_set_gif()
call doesn't look too bad.

 [ bp: Drop obscure Addresses-Coverity: tag. ]

Fixes: 6ccbd29a ("KVM: SVM: nested: Don't allocate VMCB structures on stack")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reported-by: Joerg Roedel <jroedel@suse.de>
Reported-by: Colin King <colin.king@canonical.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lkml.kernel.org/r/20200914133725.650221-1-vkuznets@redhat.comSigned-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/nested.c

@@ -1094,7 +1094,8 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
 
 	if (!(kvm_state->flags & KVM_STATE_NESTED_GUEST_MODE)) {
 		svm_leave_nested(svm);
-		goto out_set_gif;
+		svm_set_gif(svm, !!(kvm_state->flags & KVM_STATE_NESTED_GIF_SET));
+		return 0;
 	}
 
 	if (!page_address_valid(vcpu, kvm_state->hdr.svm.vmcb_pa))
@@ -1148,10 +1149,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
 	nested_prepare_vmcb_control(svm);
 
 	if (!nested_svm_vmrun_msrpm(svm))
-		return -EINVAL;
-
-out_set_gif:
-	svm_set_gif(svm, !!(kvm_state->flags & KVM_STATE_NESTED_GIF_SET));
+		goto out_free;
 
 	ret = 0;
 out_free: