Re: [PATCH v2] device property: fix of node refcount leak in fwnode_graph_get_next_endpoint()

[Yang Yingliang]

On 2022/11/22 20:54, Andy Shevchenko wrote:
> On Tue, Nov 22, 2022 at 08:00:39PM +0800, Yang Yingliang wrote:
> > The 'parent' returned by fwnode_graph_get_port_parent()
> > with refcount incremented when 'prev' is not null, it
> NULL
>
> > needs be put when finish using it.
> >
> > Because the parent is const, introduce a new variable to
> > store the returned fwnode, then put it before returning
> > from fwnode_graph_get_next_endpoint().
> ...
>
> >   fwnode_graph_get_next_endpoint(const struct fwnode_handle *fwnode,
> >   			       struct fwnode_handle *prev)
> >   {
> > +	struct fwnode_handle *ep, *port_parent = NULL;
> >   	const struct fwnode_handle *parent;
> > -	struct fwnode_handle *ep;
> >   
> >   	/*
> >   	 * If this function is in a loop and the previous iteration returned
> >   	 * an endpoint from fwnode->secondary, then we need to use the secondary
> >   	 * as parent rather than @fwnode.
> >   	 */
> > -	if (prev)
> > -		parent = fwnode_graph_get_port_parent(prev);
> > -	else
> > +	if (prev) {
> > +		port_parent = fwnode_graph_get_port_parent(prev);
> > +		parent = port_parent;
> > +	} else {
> >   		parent = fwnode;
> > +	}
> >   	if (IS_ERR_OR_NULL(parent))
> >   		return NULL;
> >   
> >   	ep = fwnode_call_ptr_op(parent, graph_get_next_endpoint, prev);
> > -	if (ep)
> > +	if (ep) {
> > +		fwnode_handle_put(port_parent);
> >   		return ep;
> > +	}
> >   
> > -	return fwnode_graph_get_next_endpoint(parent->secondary, NULL);
> > +	ep = fwnode_graph_get_next_endpoint(parent->secondary, NULL);
> > +	fwnode_handle_put(port_parent);
> > +	return ep;
> It seems too complicated for the simple fix.
>
> As I said, just drop const qualifier and add fwnode_handle_get() in the 'else'
> branch. This will allow you to drop if (prev) at the end.

fwnode is const, fwnode_handle_get doesn't accept this type.

>