Re: [PATCH] usb: gadget: f_fs: report error if excess data received

[Michal Nazarewicz]

So Iâve been looking at AIO handling in f_fs and either Iâm stupid or
the code is broken.  Hereâs part of ffs_user_copy_worker:

	int ret = io_data->req->status ? io_data->req->status :
					 io_data->req->actual;
	if (io_data->read && ret > 0) {
		use_mm(io_data->mm);
		ret = copy_to_iter(io_data->buf, ret, &io_data->data);
		if (iov_iter_count(&io_data->data))
			ret = -EFAULT;
		unuse_mm(io_data->mm);
	}

First of all, shouldnât the copy_to_iter invocation be:

		if (copy_to_iter(io_data->buf, ret, &io_data->data))
                	ret = -EFAULT;

Second of all, if the request reads fewer bytes than user requested,
iov_iter_count(â) will be non-zero (namely it will be the difference
between userâs buffer size and data read).  This should not result in
EFAULT though.

So, am I going crazy? Or does this need to be fixed as well?

-- 
Best regards
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