KVM: PPC: Book3S HV: XIVE: fix rollback when kvmppc_xive_create fails

The XIVE device structure is now allocated in kvmppc_xive_get_device()
and kfree'd in kvmppc_core_destroy_vm(). In case of an OPAL error when
allocating the XIVE VPs, the kfree() call in kvmppc_xive_*create()
will result in a double free and corrupt the host memory.

Fixes: 5422e95 ("KVM: PPC: Book3S HV: XIVE: Replace the 'destroy' method by a 'release' method")
Cc: stable@vger.kernel.org # v5.2+
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Tested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/6ea6998b-a890-2511-01d1-747d7621eb19@kaod.org

arch/powerpc/kvm/book3s_xive.c

@@ -1986,10 +1986,8 @@ static int kvmppc_xive_create(struct kvm_device *dev, u32 type)
 
 	xive->single_escalation = xive_native_has_single_escalation();
 
-	if (ret) {
-		kfree(xive);
+	if (ret)
 		return ret;
-	}
 
 	return 0;
 }

arch/powerpc/kvm/book3s_xive_native.c

@@ -1090,9 +1090,9 @@ static int kvmppc_xive_native_create(struct kvm_device *dev, u32 type)
 	xive->ops = &kvmppc_xive_native_ops;
 
 	if (ret)
-		kfree(xive);
+		return ret;
 
-	return ret;
+	return 0;
 }
 
 /*