Re: [PATCH v3] device property: fix of node refcount leak in fwnode_graph_get_next_endpoint()

[Yang Yingliang]

On 2022/11/25 17:32, Daniel Scally wrote:
> Hello
>
> On 23/11/2022 13:31, Andy Shevchenko wrote:
> > On Wed, Nov 23, 2022 at 10:25:42AM +0800, Yang Yingliang wrote:
> > > The 'parent' returned by fwnode_graph_get_port_parent()
> > > with refcount incremented when 'prev' is not NULL, it
> > > 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().
> > To me this looks good enough. Not sure if Dan has a chance (time) to look at
> > this, though. And maybe even test...
> >
> > Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
>
> Apologies; didn't notice this earlier. I will look at and test this today

Thanks,

I tested it, without this patch, I got this message:
OF: ERROR: memory leak, expected refcount 1 instead of 4, 
of_node_get()/of_node_put() unbalanced - destroy cset entry: attach 
overlay node /i2c/pmic@34/tcpc/connector
after this patch,  the message is gone.
> > > Fixes: b5b41ab6b0c1 ("device property: Check fwnode->secondary in fwnode_graph_get_next_endpoint()")
> > > Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
> > > ---
> > > v2 -> v3:
> > >    Add a out label.
> > >
> > > v1 -> v2:
> > >    Introduce a new variable to store the returned fwnode.
> > > ---
> > >   drivers/base/property.c | 18 ++++++++++++------
> > >   1 file changed, 12 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/drivers/base/property.c b/drivers/base/property.c
> > > index 2a5a37fcd998..7f338cb4fb7b 100644
> > > --- a/drivers/base/property.c
> > > +++ b/drivers/base/property.c
> > > @@ -989,26 +989,32 @@ struct fwnode_handle *
> > >   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)
> > > -		return ep;
> > > +		goto out_put_port_parent;
> > > +
> > > +	ep = fwnode_graph_get_next_endpoint(parent->secondary, NULL);
> > >   
> > > -	return fwnode_graph_get_next_endpoint(parent->secondary, NULL);
> > > +out_put_port_parent:
> > > +	fwnode_handle_put(port_parent);
> > > +	return ep;
> > >   }
> > >   EXPORT_SYMBOL_GPL(fwnode_graph_get_next_endpoint);
> > >   
> > > --
> > > 2.25.1
> .