linux-kernel - Re: [PATCH v3] device property: fix of node refcount leak in fwnode_graph_get_next

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Date:   Fri, 25 Nov 2022 17:49:11 +0800
From:   Yang Yingliang <yangyingliang@...wei.com>
To:     Daniel Scally <djrscally@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
CC:     <linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <heikki.krogerus@...ux.intel.com>, <sakari.ailus@...ux.intel.com>,
        <gregkh@...uxfoundation.org>, <rafael@...nel.org>,
        <yangyingliang@...wei.com>
Subject: Re: [PATCH v3] device property: fix of node refcount leak in
 fwnode_graph_get_next_endpoint()


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@...ux.intel.com>
>
> 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@...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@...wei.com>
>>> ---
>>> 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
>>>
> .