Q: Given the following code slice:
```
1 static void ffs_user_copy_worker(struct work_struct *work)
2 {
3 	struct ffs_io_data *io_data = container_of(work, struct ffs_io_data,
4 						   work);
5 	int ret = io_data->status;
6 	bool kiocb_has_eventfd = io_data->kiocb->ki_flags & IOCB_EVENTFD;
7 
8 	if (io_data->read && ret > 0) {
9 		kthread_use_mm(io_data->mm);
10 		ret = ffs_copy_to_iter(io_data->buf, ret, &io_data->data);
11 		kthread_unuse_mm(io_data->mm);
12 	}
13 
14 	io_data->kiocb->ki_complete(io_data->kiocb, ret, ret);
15 
16 	if (io_data->ffs->ffs_eventfd && !kiocb_has_eventfd)
17 		eventfd_signal(io_data->ffs->ffs_eventfd, 1);
18 
19 	if (io_data->read)
20 		kfree(io_data->to_free);
21 	ffs_free_buffer(io_data);
22 	kfree(io_data);
23 }
```
which has a vulnerability among CWE-457 and among lines:
```
20 		kfree(io_data->to_free);
21 	ffs_free_buffer(io_data);
22 	kfree(io_data);
```
Please generate five possible patches for the vulnerability.