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Date: Wed, 31 May 2017 10:25:47 +0200
From: Johan Hovold <johan@kernel.org>
To: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
Cc: Johan Hovold <johan@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Peter Chen <peter.chen@freescale.com>, Rob Herring <robh@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Sricharan R <sricharan@codeaurora.org>,
        Zhang Rui <rui.zhang@intel.com>,
        Eduardo Valentin <edubezval@gmail.com>, linux-pm@vger.kernel.org,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        stable <stable@vger.kernel.org>, Peter Chen <peter.chen@nxp.com>
Subject: Re: [PATCH 1/7] USB: core: fix device node leak
Message-ID: <20170531082547.GB6735@localhost>
References: <20170530162554.26159-1-johan@kernel.org>
 <20170530162554.26159-2-johan@kernel.org>
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On Tue, May 30, 2017 at 03:55:56PM -0700, Tyrel Datwyler wrote:
> 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@vger.kernel.org>	# v4.6
> > Cc: Peter Chen <peter.chen@nxp.com>
> > Signed-off-by: Johan Hovold <johan@kernel.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?

No, it may be non-NULL.

> 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.

So this one is still needed.

Thanks,
Johan