Re: [PATCH 1/2] device property: do not leak child nodes when using NULL/error pointers

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Fri, Nov 29, 2024 at 11:16:54PM -0800, Dmitry Torokhov wrote:
> On Fri, Nov 29, 2024 at 04:50:15PM +0200, Andy Shevchenko wrote:
> > On Thu, Nov 28, 2024 at 03:04:50PM -0800, Dmitry Torokhov wrote:
> > > On Thu, Nov 28, 2024 at 03:13:16PM +0200, Andy Shevchenko wrote:
> > > > On Wed, Nov 27, 2024 at 09:39:34PM -0800, Dmitry Torokhov wrote:

...

> > > > > @@ struct fwnode_handle *device_get_next_child_node(const struct device *dev,
> > > > >  	const struct fwnode_handle *fwnode = dev_fwnode(dev);
> > > > >  	struct fwnode_handle *next;
> > > > 
> > > > > -	if (IS_ERR_OR_NULL(fwnode))
> > > > > +	if (IS_ERR_OR_NULL(fwnode)) {
> > > > > +		fwnode_handle_put(child);
> > > > >  		return NULL;
> > > > > +	}
> > > > 
> > > > >  	/* Try to find a child in primary fwnode */
> > > > >  	next = fwnode_get_next_child_node(fwnode, child);
> > > > 
> > > > So, why not just moving the original check (w/o dropping the reference) here?
> > > > Wouldn't it have the same effect w/o explicit call to the fwnode_handle_put()?
> > > 
> > > Because if you rely on check in fwnode_get_next_child_node() you would
> > > not know if it returned NULL because there are no more children or
> > > because the node is invalid. In the latter case you can't dereference
> > > fwnode->secondary.
> > 
> > Yes, so, how does it contradict my proposal?
> 
> I guess I misunderstood your proposal then. Could you please explain it
> in more detail?


Current code (in steps):
	if (IS_ERR_OR_NULL()) check
	trying primary
	trying secondary if previous is NULL


My proposal

	trying primary
	return if not NULL
	if (IS_ERR_OR_NULL()) check in its current form (no put op)
	trying secondary

After your first patch IIUC this is possible as trying primary will put child uncoditionally.

-- 
With Best Regards,
Andy Shevchenko