xen/privcmd: Use memdup_array_user() in alloc_ioreq()

* The function “memdup_array_user” was added with the
  commit 313ebe47 ("string.h: add
  array-wrappers for (v)memdup_user()").
  Thus use it accordingly.

  This issue was detected by using the Coccinelle software.

* Delete a label which became unnecessary with this refactoring.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/41e333f7-1f3a-41b6-a121-a3c0ae54e36f@web.deSigned-off-by: Juergen Gross <jgross@suse.com>

drivers/xen/privcmd.c

@@ -1223,18 +1223,13 @@ struct privcmd_kernel_ioreq *alloc_ioreq(struct privcmd_ioeventfd *ioeventfd)
 	kioreq->ioreq = (struct ioreq *)(page_to_virt(pages[0]));
 	mmap_write_unlock(mm);
 
-	size = sizeof(*ports) * kioreq->vcpus;
-	ports = kzalloc(size, GFP_KERNEL);
-	if (!ports) {
-		ret = -ENOMEM;
+	ports = memdup_array_user(u64_to_user_ptr(ioeventfd->ports),
+				  kioreq->vcpus, sizeof(*ports));
+	if (IS_ERR(ports)) {
+		ret = PTR_ERR(ports);
 		goto error_kfree;
 	}
 
-	if (copy_from_user(ports, u64_to_user_ptr(ioeventfd->ports), size)) {
-		ret = -EFAULT;
-		goto error_kfree_ports;
-	}
-
 	for (i = 0; i < kioreq->vcpus; i++) {
 		kioreq->ports[i].vcpu = i;
 		kioreq->ports[i].port = ports[i];
@@ -1256,7 +1251,7 @@ struct privcmd_kernel_ioreq *alloc_ioreq(struct privcmd_ioeventfd *ioeventfd)
 error_unbind:
 	while (--i >= 0)
 		unbind_from_irqhandler(irq_from_evtchn(ports[i]), &kioreq->ports[i]);
-error_kfree_ports:
+
 	kfree(ports);
 error_kfree:
 	kfree(kioreq);