Re: [PATCH 15/23] interconnect: exynos: fix registration race

[Krzysztof Kozlowski]

On 01/02/2023 11:15, Johan Hovold wrote:
> The current interconnect provider registration interface is inherently
> racy as nodes are not added until the after adding the provider. This
> can specifically cause racing DT lookups to trigger a NULL-pointer
> deference when either a NULL pointer or not fully initialised node is
> returned from exynos_generic_icc_xlate().
> 
> Switch to using the new API where the provider is not registered until
> after it has been fully initialised.
> 
> Fixes: 2f95b9d5cf0b ("interconnect: Add generic interconnect driver for Exynos SoCs")
> Cc: stable@xxxxxxxxxxxxxxx      # 5.11
> Cc: Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx>
> Signed-off-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
> ---
>  drivers/interconnect/samsung/exynos.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/interconnect/samsung/exynos.c b/drivers/interconnect/samsung/exynos.c
> index e70665899482..72e42603823b 100644
> --- a/drivers/interconnect/samsung/exynos.c
> +++ b/drivers/interconnect/samsung/exynos.c
> @@ -98,12 +98,13 @@ static int exynos_generic_icc_remove(struct platform_device *pdev)
>  	struct exynos_icc_priv *priv = platform_get_drvdata(pdev);
>  	struct icc_node *parent_node, *node = priv->node;
>  
> +	icc_provider_deregister(&priv->provider);
> +
>  	parent_node = exynos_icc_get_parent(priv->dev->parent->of_node);
>  	if (parent_node && !IS_ERR(parent_node))
>  		icc_link_destroy(node, parent_node);
>  
>  	icc_nodes_remove(&priv->provider);
> -	icc_provider_del(&priv->provider);
>  
>  	return 0;
>  }
> @@ -132,15 +133,11 @@ static int exynos_generic_icc_probe(struct platform_device *pdev)
>  	provider->inter_set = true;
>  	provider->data = priv;
>  
> -	ret = icc_provider_add(provider);
> -	if (ret < 0)
> -		return ret;
> +	icc_provider_init(provider);
>  
>  	icc_node = icc_node_create(pdev->id);
> -	if (IS_ERR(icc_node)) {
> -		ret = PTR_ERR(icc_node);
> -		goto err_prov_del;
> -	}
> +	if (IS_ERR(icc_node))
> +		return PTR_ERR(icc_node);
>  
>  	priv->node = icc_node;
>  	icc_node->name = devm_kasprintf(&pdev->dev, GFP_KERNEL, "%pOFn",
> @@ -171,14 +168,17 @@ static int exynos_generic_icc_probe(struct platform_device *pdev)
>  			goto err_pmqos_del;
>  	}
>  
> +	ret = icc_provider_register(provider);
> +	if (ret < 0)
> +		goto err_pmqos_del;

If I understand correctly there is no need for icc_link_destroy() in
error path here, right? Even in case of probe retry (defer or whatever
reason) - the link will be removed with icc_nodes_remove()?

Best regards,
Krzysztof