linux-kernel - Re: [PATCH v4 4/6] phy: core: Fix an OF node refcount leakage in _of_phy

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Message-ID: <ZypT18RpHSd_Vb-o@hovoldconsulting.com>
Date: Tue, 5 Nov 2024 18:20:23 +0100
From: Johan Hovold <johan@...nel.org>
To: Zijun Hu <zijun_hu@...oud.com>
Cc: Vinod Koul <vkoul@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Rob Herring <robh@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Lee Jones <lee@...nel.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	stable@...r.kernel.org, linux-phy@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Zijun Hu <quic_zijuhu@...cinc.com>
Subject: Re: [PATCH v4 4/6] phy: core: Fix an OF node refcount leakage in
 _of_phy_get()

On Sat, Nov 02, 2024 at 11:53:46AM +0800, Zijun Hu wrote:
> From: Zijun Hu <quic_zijuhu@...cinc.com>
> 
> _of_phy_get() will directly return when suffers of_device_is_compatible()
> error, but it forgets to decrease refcount of OF node @args.np before error
> return, the refcount was increased by previous of_parse_phandle_with_args()
> so causes the OF node's refcount leakage.
> 
> Fix by decreasing the refcount via of_node_put() before the error return.
> 
> Fixes: b7563e2796f8 ("phy: work around 'phys' references to usb-nop-xceiv devices")
> Cc: stable@...r.kernel.org
> Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
> ---
>  drivers/phy/phy-core.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
> index 52ca590a58b9..3127c5d9c637 100644
> --- a/drivers/phy/phy-core.c
> +++ b/drivers/phy/phy-core.c
> @@ -624,13 +624,15 @@ static struct phy *_of_phy_get(struct device_node *np, int index)
>  	struct of_phandle_args args;
>  
>  	ret = of_parse_phandle_with_args(np, "phys", "#phy-cells",
> -		index, &args);
> +					 index, &args);

This is an unrelated change which do not belong in this patch (and even
more so as it is a fix that is marked for backporting).

>  	if (ret)
>  		return ERR_PTR(-ENODEV);
>  
>  	/* This phy type handled by the usb-phy subsystem for now */
> -	if (of_device_is_compatible(args.np, "usb-nop-xceiv"))
> -		return ERR_PTR(-ENODEV);
> +	if (of_device_is_compatible(args.np, "usb-nop-xceiv")) {
> +		phy = ERR_PTR(-ENODEV);
> +		goto out_put_node;
> +	}
>  
>  	mutex_lock(&phy_provider_mutex);
>  	phy_provider = of_phy_provider_lookup(args.np);
> @@ -652,6 +654,7 @@ static struct phy *_of_phy_get(struct device_node *np, int index)
>  
>  out_unlock:
>  	mutex_unlock(&phy_provider_mutex);
> +out_put_node:
>  	of_node_put(args.np);
>  
>  	return phy;A

With the above fixed:

Reviewed-by: Johan Hovold <johan+linaro@...nel.org>