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 15:50:53 +0000
From:   Daniel Scally <djrscally@...il.com>
To:     Yang Yingliang <yangyingliang@...wei.com>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     andriy.shevchenko@...ux.intel.com, heikki.krogerus@...ux.intel.com,
        sakari.ailus@...ux.intel.com, gregkh@...uxfoundation.org,
        rafael@...nel.org
Subject: Re: [PATCH v3] device property: fix of node refcount leak in
 fwnode_graph_get_next_endpoint()

Hi all - sorry that took so long

On 23/11/2022 02:25, 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().
>
> Fixes: b5b41ab6b0c1 ("device property: Check fwnode->secondary in fwnode_graph_get_next_endpoint()")
> Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
> ---


This looks fine to me (thanks for fixing it), and it works fine on my
Surface:


Reviewed-and-tested-by: Daniel Scally <djrscally@...il.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);
>