netdev - Re: [PATCH -next] net: pcs: Add missing put_device call in miic

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Date: Tue, 8 Aug 2023 13:53:17 +0300
From: Vladimir Oltean <olteanv@...il.com>
To: Xiang Yang <xiangyang@...weicloud.com>
Cc: clement.leger@...tlin.com, hkallweit1@...il.com, linux@...linux.org.uk,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, f.fainelli@...il.com,
	linux-renesas-soc@...r.kernel.org, netdev@...r.kernel.org,
	xiangyang3@...wei.com
Subject: Re: [PATCH -next] net: pcs: Add missing put_device call in
 miic_create

On Mon, Aug 07, 2023 at 01:47:14PM +0000, Xiang Yang wrote:
> From: Xiang Yang <xiangyang3@...wei.com>
> 
> The reference of pdev->dev is taken by of_find_device_by_node, so
> it should be released when error out.
> 
> Fixes: 7dc54d3b8d91 ("net: pcs: add Renesas MII converter driver")
> Signed-off-by: Xiang Yang <xiangyang3@...wei.com>
> ---

Ok, but if of_find_device_by_node() requires a subsequent call to
put_device(), then doesn't this mean that in the non-error case, the
pdev refcount remains elevated, and will thus never be freed?

I would expect another put_device(&pdev->dev) after the device_link_add(),
which itself takes another set of references on the supplier and
consumer devs, which are sufficient for this driver's runtime operation.

Also, "if (!pdev)" and "if (!platform_get_drvdata(pdev)" here need
different treatment. One needs to call put_device(&pdev->dev) and the
other one doesn't.

	pdev = of_find_device_by_node(pcs_np);
	of_node_put(pcs_np);
	if (!pdev || !platform_get_drvdata(pdev))
		return ERR_PTR(-EPROBE_DEFER);

pw-bot: cr

>  drivers/net/pcs/pcs-rzn1-miic.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/pcs/pcs-rzn1-miic.c b/drivers/net/pcs/pcs-rzn1-miic.c
> index e5d642c67a2c..d097f123635a 100644
> --- a/drivers/net/pcs/pcs-rzn1-miic.c
> +++ b/drivers/net/pcs/pcs-rzn1-miic.c
> @@ -318,8 +318,10 @@ struct phylink_pcs *miic_create(struct device *dev, struct device_node *np)
>  		return ERR_PTR(-EPROBE_DEFER);
>  
>  	miic_port = kzalloc(sizeof(*miic_port), GFP_KERNEL);
> -	if (!miic_port)
> +	if (!miic_port) {
> +		put_device(&pdev->dev);
>  		return ERR_PTR(-ENOMEM);
> +	}
>  
>  	miic = platform_get_drvdata(pdev);
>  	device_link_add(dev, miic->dev, DL_FLAG_AUTOREMOVE_CONSUMER);
> -- 
> 2.34.1
>