diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index cf88233b819a..68edd25dcb11 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4350,10 +4350,10 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
 	new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
 			  GFP_KERNEL_ACCOUNT);
 	if (new_bus) {
-		memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range));
+		memcpy(new_bus, bus, struct_size(bus, range, i));
 		new_bus->dev_count--;
 		memcpy(new_bus->range + i, bus->range + i + 1,
-		       (new_bus->dev_count - i) * sizeof(struct kvm_io_range));
+				flex_array_size(new_bus, range, new_bus->dev_count - i));
 	} else {
 		pr_err("kvm: failed to shrink bus, removing it completely\n");
 		for (j = 0; j < bus->dev_count; j++) {