Re: [PATCH] net: mdio: fix unbalanced fwnode reference count in mdio_device_release()

[Yang Yingliang <yangyingliang@huawei.com>]

On 2022/12/1 17:22, Zeng Heng wrote:
> There is warning report about of_node refcount leak
> while probing mdio device:
>
> OF: ERROR: memory leak, expected refcount 1 instead of 2,
> of_node_get()/of_node_put() unbalanced - destroy cset entry:
> attach overlay node /spi/soc@0/mdio@710700c0/ethernet@4
>
> In of_mdiobus_register_device(), we increase fwnode refcount
> by fwnode_handle_get() before associating the of_node with
> mdio device, but it has never been decreased after that.
> Since that, in mdio_device_release(), it needs to call
> fwnode_handle_put() in addition instead of calling kfree()
> directly.
>
> After above, just calling mdio_device_free() in the error handle
> path of of_mdiobus_register_device() is enough to keep the
> refcount balanced.
>
> Fixes: a9049e0c513c ("mdio: Add support for mdio drivers.")
> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
> ---
>   drivers/net/mdio/of_mdio.c    | 1 -
>   drivers/net/phy/mdio_device.c | 2 ++
>   2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/mdio/of_mdio.c b/drivers/net/mdio/of_mdio.c
> index 796e9c7857d0..296317a6b333 100644
> --- a/drivers/net/mdio/of_mdio.c
> +++ b/drivers/net/mdio/of_mdio.c
> @@ -69,7 +69,6 @@ static int of_mdiobus_register_device(struct mii_bus *mdio,
>   	rc = mdio_device_register(mdiodev);
>   	if (rc) {
>   		mdio_device_free(mdiodev);
> -		of_node_put(child);
device_set_node() is called to set fwnode and of_node, for undoing this,
calling device_set_node(NULL) is better, and then call the put function.

Thanks,
Yang
>   		return rc;
>   	}
>   
> diff --git a/drivers/net/phy/mdio_device.c b/drivers/net/phy/mdio_device.c
> index 250742ffdfd9..044828d081d2 100644
> --- a/drivers/net/phy/mdio_device.c
> +++ b/drivers/net/phy/mdio_device.c
> @@ -21,6 +21,7 @@
>   #include <linux/slab.h>
>   #include <linux/string.h>
>   #include <linux/unistd.h>
> +#include <linux/property.h>
>   
>   void mdio_device_free(struct mdio_device *mdiodev)
>   {
> @@ -30,6 +31,7 @@ EXPORT_SYMBOL(mdio_device_free);
>   
>   static void mdio_device_release(struct device *dev)
>   {
> +	fwnode_handle_put(dev->fwnode);
>   	kfree(to_mdio_device(dev));
>   }
>