linux-kernel - Re: [PATCH] USB: input: gtco.c: fix usb

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Message-ID: <20140127065416.GA11945@core.coreip.homeip.net>
Date:	Sun, 26 Jan 2014 22:54:16 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Alexey Khoroshilov <khoroshilov@...ras.ru>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	ldv-project@...uxtesting.org
Subject: Re: [PATCH] USB: input: gtco.c: fix usb_dev leak

Hi Alexey,

On Mon, Jan 27, 2014 at 10:31:36AM +0400, Alexey Khoroshilov wrote:
> On 21.01.2014 23:59, Dmitry Torokhov wrote:
> > On Sun, Jan 19, 2014 at 03:24:26AM +0400, Alexey Khoroshilov wrote:
> >> There is usb_get_dev() in gtco_probe(), but there is no usb_put_dev()
> >> anywhere in the driver.
> >>
> >> The patch adds usb_get_dev() to failure handling code of gtco_probe()
> >> and to gtco_disconnect(().
> > Hmm, I think gtco should simply not use usb_get_dev() in the first
> > place.
> >
> > Thanks.
> Dear Dmitry,
> 
> Could you please clarify why usb_get_dev() not needed here?
> We store reference to usb_dev in gtco structure, so we should refcount it.
> What is wrong in this reasoning?

The lifetime of gtco structure is already directly tied to lifetime of
usb_dev: when destroying usb_dev driver core will call remove() function
of currently bound driver (in our case gtco) which will destroy gtco
memory.

Taking additional reference is not needed here.

Hope this helps.

-- 
Dmitry
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