usb: gadget: composite: prevent a memory leak when configuration bind fails

In some USB composite gadget drivers, the configuration's bind function called
by the usb_add_config() calls multiple bind config functions. (for example cdc2
configuration bind function in the cdc_do_config() of the cdc2.c has two
functionality bind config functions.
  - the ecm_bind_config() & the acm_bind_config())

In each functionality bind config function, new instance is allocated and
finally added by the usb_add_function().

So if an error occurred during the second functionality bind config (for
example an error occurred at the acm_bind_config() after succeeding of the
ecm_bind_function()), the instance created by the acm_bind_config() cannot be
freed creating a memory leak.

This patch fixes this issue.
Signed-off-by: Yongsul Oh <yongsul96.oh@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/composite.c

@@ -737,6 +737,19 @@ int usb_add_config(struct usb_composite_dev *cdev,
 
 	status = bind(config);
 	if (status < 0) {
+		while (!list_empty(&config->functions)) {
+			struct usb_function		*f;
+
+			f = list_first_entry(&config->functions,
+					struct usb_function, list);
+			list_del(&f->list);
+			if (f->unbind) {
+				DBG(cdev, "unbind function '%s'/%p\n",
+					f->name, f);
+				f->unbind(config, f);
+				/* may free memory for "f" */
+			}
+		}
 		list_del(&config->list);
 		config->cdev = NULL;
 	} else {