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

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Message-ID: <52E63503.3060804@ispras.ru>
Date:	Mon, 27 Jan 2014 14:29:23 +0400
From:	Alexey Khoroshilov <khoroshilov@...ras.ru>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	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

On 27.01.2014 10:54, Dmitry Torokhov wrote:
> 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.
Thank you, that helps a lot.

By the way, usb_skeleton suggests to use usb_get_dev()/usb_put_dev()
nevertheless.

Greg, may be it makes sense to fix usb_skeleton as well?

--
Alexey
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