KVM: Use kmemdup() instead of kmalloc/memcpy

Switch to kmemdup() in two places to shorten the code and avoid possible bugs.
Signed-off-by: NSasha Levin <levinsasha928@gmail.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

arch/x86/kvm/x86.c

@@ -3031,10 +3031,10 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 		memset(dirty_bitmap_head, 0, n);
 
 		r = -ENOMEM;
-		slots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
+		slots = kmemdup(kvm->memslots, sizeof(*kvm->memslots), GFP_KERNEL);
 		if (!slots)
 			goto out;
-		memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
+
 		memslot = id_to_memslot(slots, log->slot);
 		memslot->nr_dirty_pages = 0;
 		memslot->dirty_bitmap = dirty_bitmap_head;

virt/kvm/kvm_main.c

@@ -2591,13 +2591,12 @@ int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
 	int i, r;
 	struct kvm_io_bus *new_bus, *bus;
 
-	new_bus = kzalloc(sizeof(struct kvm_io_bus), GFP_KERNEL);
+	bus = kvm->buses[bus_idx];
+
+	new_bus = kmemdup(bus, sizeof(*bus), GFP_KERNEL);
 	if (!new_bus)
 		return -ENOMEM;
 
-	bus = kvm->buses[bus_idx];
-	memcpy(new_bus, bus, sizeof(struct kvm_io_bus));
-
 	r = -ENOENT;
 	for (i = 0; i < new_bus->dev_count; i++)
 		if (new_bus->range[i].dev == dev) {