netdev - Re: [PATCH] p54usb: fix leaks at failure path in p54u

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Date:	Sun, 9 Mar 2014 04:40:58 +0530
From:	Krishna Chaitanya <chaitanya.mgit@...il.com>
To:	Christian Lamparter <chunkeey@...glemail.com>
Cc:	Alexey Khoroshilov <khoroshilov@...ras.ru>,
	"John W. Linville" <linville@...driver.com>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org,
	ldv-project@...uxtesting.org
Subject: Re: [PATCH] p54usb: fix leaks at failure path in p54u_probe()

On Sun, Mar 9, 2014 at 4:38 AM, Christian Lamparter
<chunkeey@...glemail.com> wrote:
> On Sunday, March 09, 2014 04:14:32 AM Krishna Chaitanya wrote:
>> On Sat, Mar 8, 2014 at 2:41 AM, Alexey Khoroshilov
>> <khoroshilov@...ras.ru> wrote:
>> > If p54u_load_firmware() fails, p54u_probe() does not deallocate
>> > already allocated resources. The patch adds proper failure handling.
>> >
>> > Found by Linux Driver Verification project (linuxtesting.org).
>> >
>> > Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
>> > ---
>> >  drivers/net/wireless/p54/p54usb.c | 4 ++++
>> >  1 file changed, 4 insertions(+)
>> >
>> > diff --git a/drivers/net/wireless/p54/p54usb.c b/drivers/net/wireless/p54/p54usb.c
>> > index 6e635cfa24c8..5df74503fd4f 100644
>> > --- a/drivers/net/wireless/p54/p54usb.c
>> > +++ b/drivers/net/wireless/p54/p54usb.c
>> > @@ -1053,6 +1053,10 @@ static int p54u_probe(struct usb_interface *intf,
>> >                 priv->upload_fw = p54u_upload_firmware_net2280;
>> >         }
>> >         err = p54u_load_firmware(dev, intf);
>> > +       if (err) {
>> > +               usb_put_dev(udev);
>> > +               p54_free_common(dev);
>> > +       }
>> >         return err;
>> >  }
>> The load_firmware puts down the reference
>> in case of error. Only free is required here.
> No, the put is required too... But let me explain:
>
> p54u_load_firmware calls usb_get_dev(udev) before it requests the firmware
> load. The Reason is: the firmware callback is usually run in another thread
> (usually it's pretty quick, but due to timeouts it could take up to 60 seconds
> - or at least it did when I wrote it). Therefore I found it appropriate to give
> that request callback its "reference++" as it needs the "udev" too (e.g.: for
> dev_info, dev_err and releasing the driver if the device couldn't be
> initialized).
>
Thanks Christian and Alexey, you answered my next question as well :-).
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