linux-kernel - Re: [PATCH 2/3] Add rfkill support to compal-laptop

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Date:	Tue, 18 Aug 2009 15:52:18 +0100
From:	Alan Jenkins <sourcejedi.lkml@...glemail.com>
To:	Marcel Holtmann <marcel@...tmann.org>
Cc:	Mario Limonciello <mario_limonciello@...l.com>,
	cezary.jackiewicz@...il.com, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] Add rfkill support to compal-laptop

On 8/18/09, Alan Jenkins <sourcejedi.lkml@...glemail.com> wrote:
> On 8/18/09, Marcel Holtmann <marcel@...tmann.org> wrote:
>> Hi Mario,
>
> ...
>
>>> +static int setup_rfkill(void)
>>> +{
>>> +       int ret;
>>> +
>>> +       wifi_rfkill = rfkill_alloc("compal-wifi", NULL,
>>> RFKILL_TYPE_WLAN,
>>> +                                       &compal_rfkill_ops, (void *)
>>> WLAN_MASK);
>>> +       if (!wifi_rfkill) {
>>> +               ret = -ENOMEM;
>>> +               goto err_wifi;
>>> +       }
>>> +       ret = rfkill_register(wifi_rfkill);
>>> +       if (ret)
>>> +               goto err_wifi;
>>> +
>>> +       bluetooth_rfkill = rfkill_alloc("compal-bluetooth", NULL,
>>> RFKILL_TYPE_BLUETOOTH,
>>> +                                       &compal_rfkill_ops, (void *)
>>> BT_MASK);
>>> +       if (!bluetooth_rfkill) {
>>> +               ret = -ENOMEM;
>>> +               goto err_bt;
>>> +       }
>>> +       ret = rfkill_register(bluetooth_rfkill);
>>> +       if (ret)
>>> +               goto err_bt;
>>> +
>>> +       return 0;
>>> +err_bt:
>>> +       rfkill_destroy(bluetooth_rfkill);
>>> +       if (bluetooth_rfkill)
>>> +               rfkill_unregister(bluetooth_rfkill);
>>> +err_wifi:
>>> +       rfkill_destroy(wifi_rfkill);
>>> +       if (wifi_rfkill)
>>> +               rfkill_unregister(wifi_rfkill);
>>
>> I don't understand how this is not a potential NULL pointer dereference.
>> There might some good luck that the pointer is still valid at that time,
>> but I highly doubt it. So please unregister before destory.
>
> Wrong as well :-).
>
> If you fail to register wifi_rfkill, you should *only* call
> rfkill_destroy().  So I think it should look like this:
>
> +       if (wifi_rfkill)
> +               rfkill_unregister(wifi_rfkill);
> +err_wifi:
> +       rfkill_destroy(wifi_rfkill);
>
> ...
>
>>> @@ -420,6 +518,10 @@
>>>         platform_device_unregister(compal_device);
>>>         platform_driver_unregister(&compal_driver);
>>>         backlight_device_unregister(compalbl_device);
>>> +       if (wifi_rfkill)
>>> +               rfkill_unregister(wifi_rfkill);
>>> +       if (bluetooth_rfkill)
>>> +               rfkill_unregister(bluetooth_rfkill);
>>
>> Same here. It should never ever succeeded in the first place. You can
>> call it conditionally.
>
> They're already called conditionally.  I assume you mean unconditionally
> here.

Also, you're missing the calls to rfkill_destroy() here.

Whew, I think that's everything.  I hope you find the feedback useful,
despite it being a little fragmented.

Regards
Alan
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