linux-kernel - Re: [PATCH 1/7] USB: core: fix device node leak

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Message-Id: <9aff0d42-ff3e-963a-7aaa-752c2f592d0d@linux.vnet.ibm.com>
Date:   Tue, 30 May 2017 15:55:56 -0700
From:   Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>
To:     Johan Hovold <johan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Peter Chen <peter.chen@...escale.com>,
        Rob Herring <robh@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Sricharan R <sricharan@...eaurora.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>,
        linux-pm@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable <stable@...r.kernel.org>,
        Peter Chen <peter.chen@....com>
Subject: Re: [PATCH 1/7] USB: core: fix device node leak

On 05/30/2017 09:25 AM, Johan Hovold wrote:
> Make sure to release any OF device-node reference taken when creating
> the USB device.
> 
> Note that we currently do not hold a reference to the root hub
> device-tree node (i.e. the parent controller node).
> 
> Fixes: 69bec7259853 ("USB: core: let USB device know device node")
> Cc: stable <stable@...r.kernel.org>	# v4.6
> Cc: Peter Chen <peter.chen@....com>
> Signed-off-by: Johan Hovold <johan@...nel.org>
> ---
>  drivers/usb/core/usb.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
> index 28b053cacc90..62e1906bb2f3 100644
> --- a/drivers/usb/core/usb.c
> +++ b/drivers/usb/core/usb.c
> @@ -416,6 +416,8 @@ static void usb_release_dev(struct device *dev)
>  
>  	usb_destroy_configuration(udev);
>  	usb_release_bos_descriptor(udev);
> +	if (udev->parent)
> +		of_node_put(dev->of_node);

If I'm following the root hub doesn't hold an of_node reference, so does that guarantee
that dev->of_node is NULL for the root hub? If so of_node_put() is safely called with a
NULL reference, making the if(udev->parent) unnecessary, and further no need to remove it
in follow-up patch #5.

-Tyrel

>  	usb_put_hcd(hcd);
>  	kfree(udev->product);
>  	kfree(udev->manufacturer);
>