Re: [PATCH v2] net: dsa: bcm_sf2: Fix possible memory leak in bcm_sf2_mdio_register()

[Florian Fainelli <florian.fainelli@broadcom.com>]

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On 10/10/23 11:05, Simon Horman wrote:
> On Mon, Oct 09, 2023 at 04:39:06PM +0800, Jinjie Ruan wrote:
>> In bcm_sf2_mdio_register(), the class_find_device() will call get_device()
>> to increment reference count for priv->master_mii_bus->dev if
>> of_mdio_find_bus() succeeds. If mdiobus_alloc() or mdiobus_register()
>> fails, it will call get_device() twice without decrement reference count
>> for the device. And it is the same if bcm_sf2_mdio_register() succeeds but
>> fails in bcm_sf2_sw_probe(), or if bcm_sf2_sw_probe() succeeds. If the
>> reference count has not decremented to zero, the dev related resource will
>> not be freed.
>>
>> So remove the get_device() in bcm_sf2_mdio_register(), and call
>> put_device() if mdiobus_alloc() or mdiobus_register() fails and in
>> bcm_sf2_mdio_unregister() to solve the issue.
>>
>> Fixes: 461cd1b03e32 ("net: dsa: bcm_sf2: Register our slave MDIO bus")
>> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> 
> Hi Jinjie Ruan,
> 
> I agree with your analysis here, but I wonder if it would be nicer
> to move bcm_sf2_mdio_register() to a more idiomatic way of unwinding
> from errors.

That would appear a tad cleaner, yes!

> 
> Something like this (compile tested only!)
> 
> diff --git a/drivers/net/dsa/bcm_sf2.c b/drivers/net/dsa/bcm_sf2.c
> index 0b62bd78ac50..037ce118ee00 100644
> --- a/drivers/net/dsa/bcm_sf2.c
> +++ b/drivers/net/dsa/bcm_sf2.c
> @@ -617,8 +617,8 @@ static int bcm_sf2_mdio_register(struct dsa_switch *ds)
>   	dn = of_find_compatible_node(NULL, NULL, "brcm,unimac-mdio");
>   	priv->master_mii_bus = of_mdio_find_bus(dn);
>   	if (!priv->master_mii_bus) {
> -		of_node_put(dn);
> -		return -EPROBE_DEFER;
> +		err = -EPROBE_DEFER;
> +		goto err_of_node_put;
>   	}
>   
>   	get_device(&priv->master_mii_bus->dev);
> @@ -626,8 +626,8 @@ static int bcm_sf2_mdio_register(struct dsa_switch *ds)
>   
>   	priv->slave_mii_bus = mdiobus_alloc();
>   	if (!priv->slave_mii_bus) {
> -		of_node_put(dn);
> -		return -ENOMEM;
> +		err = -ENOMEM;
> +		goto err_put_master_mii_bus_device;
>   	}
>   
>   	priv->slave_mii_bus->priv = priv;
> @@ -684,12 +684,18 @@ static int bcm_sf2_mdio_register(struct dsa_switch *ds)
>   	}
>   
>   	err = mdiobus_register(priv->slave_mii_bus);
> -	if (err && dn) {
> -		mdiobus_free(priv->slave_mii_bus);
> -		of_node_put(dn);
> -	}
> +	if (err && dn)
> +		goto err_free_slave_mii_bus;
>   
>   	return err;
> +
> +err_free_slave_mii_bus:
> +	mdiobus_free(priv->slave_mii_bus);
> +err_put_master_mii_bus_device:
> +	put_device(&priv->master_mii_bus->dev);
> +err_of_node_put:
> +	of_node_put(dn);
> +	return err;
>   }
>   
>   static void bcm_sf2_mdio_unregister(struct bcm_sf2_priv *priv)

-- 
Florian


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