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

[Felipe Balbi]

Hi again,

Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx> writes:
> @@ -811,7 +815,12 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
>  		 */
>  		ret = interrupted ? -EINTR : ep->status;
>  		if (io_data->read && ret > 0) {
> -			ret = copy_to_iter(data, ret, &io_data->data);
> +			if (ret > io_data->expected_len)
> +				pr_debug("FFS: size mismatch: %zd for %zd",
> +						ret, io_data->expected_len);
> +
> +			ret = copy_to_iter(data, io_data->expected_len,
> +					&io_data->data);

we need a min() here. Better version below:

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 73515d54e1cc..6c49b152f46e 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -156,6 +156,8 @@ struct ffs_io_data {
 	struct usb_request *req;
 
 	struct ffs_data *ffs;
+
+	ssize_t expected_len;
 };
 
 struct ffs_desc_helper {
@@ -730,8 +732,10 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 		 * Controller may require buffer size to be aligned to
 		 * maxpacketsize of an out endpoint.
 		 */
-		if (io_data->read)
+		if (io_data->read) {
+			io_data->expected_len = data_len;
 			data_len = usb_ep_align_maybe(gadget, ep->ep, data_len);
+		}
 		spin_unlock_irq(&epfile->ffs->eps_lock);
 
 		data = kmalloc(data_len, GFP_KERNEL);
@@ -811,7 +815,15 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 		 */
 		ret = interrupted ? -EINTR : ep->status;
 		if (io_data->read && ret > 0) {
-			ret = copy_to_iter(data, ret, &io_data->data);
+			ssize_t bytes;
+
+			if (ret > io_data->expected_len)
+				pr_debug("FFS: size mismatch: %zd for %zd",
+						ret, io_data->expected_len);
+
+			bytes = min(ret, io_data->expected_len);
+
+			ret = copy_to_iter(data, bytes, &io_data->data);
 			if (!ret)
 				ret = -EFAULT;
 		}


-- 
balbi