usbip: tools: Fix read_usb_vudc_device() error path handling

This isn't really accurate right. fread() doesn't always
return 0 in error. It could return < number of elements
and set errno.
Signed-off-by: GwanYeong Kim <gy741.kim@gmail.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/20191018032223.4644-1-gy741.kim@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tools/usb/usbip/libsrc/usbip_device_driver.c

@@ -69,7 +69,7 @@ int read_usb_vudc_device(struct udev_device *sdev, struct usbip_usb_device *dev)
 	FILE *fd = NULL;
 	struct udev_device *plat;
 	const char *speed;
-	int ret = 0;
+	size_t ret;
 
 	plat = udev_device_get_parent(sdev);
 	path = udev_device_get_syspath(plat);
@@ -79,8 +79,10 @@ int read_usb_vudc_device(struct udev_device *sdev, struct usbip_usb_device *dev)
 	if (!fd)
 		return -1;
 	ret = fread((char *) &descr, sizeof(descr), 1, fd);
-	if (ret < 0)
+	if (ret != 1) {
+		err("Cannot read vudc device descr file: %s", strerror(errno));
 		goto err;
+	}
 	fclose(fd);
 
 	copy_descr_attr(dev, &descr, bDeviceClass);