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

[Michal Nazarewicz <mina86@mina86.com>]

So I’ve been looking at AIO handling in f_fs and either I’m stupid or
the code is broken.  Here’s 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, shouldn’t 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(…) will be non-zero (namely it will be the difference
between user’s 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
ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
«If at first you don’t succeed, give up skydiving»