linux-kernel - Re: [PATCH] leds-gpio: Fix error handling and memory leak

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Message-ID: <551C5D30.6060608@mvista.com>
Date:	Wed, 01 Apr 2015 16:03:44 -0500
From:	Corey Minyard <cminyard@...sta.com>
To:	Bryan Wu <cooloney@...il.com>, minyard@....org
CC:	Raphael Assenat <raph@...com>,
	Linux LED Subsystem <linux-leds@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] leds-gpio: Fix error handling and memory leak

Sorry, I'm traveling and it's been rather busy.

I thought about this some more, and I've realized that the devm_kfree()
calls are probably still a good idea.  Those are associated with the
device, not the LED.

For instance, I noticed that on a failure in the probe code the probe
code would get called multiple times.  So that data would be left in the
device, even though it's not used.

Similarly, the pdev doesn't go away if you remove the led-gpio module
and then re-install it.  Again, the data would be left in the device.

Does that make sense?  If so, the original patch is best.

-corey

On 03/30/2015 05:16 PM, Bryan Wu wrote:
> On Thu, Mar 26, 2015 at 8:08 PM, Corey Minyard <minyard@....org> wrote:
>> On 03/26/2015 08:20 PM, Bryan Wu wrote:
>>> On Mon, Mar 9, 2015 at 5:43 PM,  <minyard@....org> wrote:
>>>> From: Corey Minyard <cminyard@...sta.com>
>>>>
>>>> The leds-gpio driver would not clean up properly if it failed in some
>>>> places, and it wasn't freeing its private data.
>>>>
>>>> Signed-off-by: Corey Minyard <cminyard@...sta.com>
>>>> ---
>>>>  drivers/leds/leds-gpio.c | 13 +++++++++----
>>>>  1 file changed, 9 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/leds/leds-gpio.c b/drivers/leds/leds-gpio.c
>>>> index d26af0a..32f7642 100644
>>>> --- a/drivers/leds/leds-gpio.c
>>>> +++ b/drivers/leds/leds-gpio.c
>>>> @@ -198,8 +198,10 @@ static struct gpio_leds_priv *gpio_leds_create(struct platform_device *pdev)
>>>>                 } else {
>>>>                         if (IS_ENABLED(CONFIG_OF) && !led.name && np)
>>>>                                 led.name = np->name;
>>>> -                       if (!led.name)
>>>> -                               return ERR_PTR(-EINVAL);
>>>> +                       if (!led.name) {
>>>> +                               ret = -EINVAL;
>>>> +                               goto err;
>>>> +                       }
>>>>                 }
>>>>                 fwnode_property_read_string(child, "linux,default-trigger",
>>>>                                             &led.default_trigger);
>>>> @@ -217,19 +219,21 @@ static struct gpio_leds_priv *gpio_leds_create(struct platform_device *pdev)
>>>>                 if (fwnode_property_present(child, "retain-state-suspended"))
>>>>                         led.retain_state_suspended = 1;
>>>>
>>>> -               ret = create_gpio_led(&led, &priv->leds[priv->num_leds++],
>>>> +               ret = create_gpio_led(&led, &priv->leds[priv->num_leds],
>>> Why need this change? it's correct. And your add one more line
>>> "priv->num_leds++"
>> That's actually the major source of the problem.  The value of
>> priv->num_leds was not correct if it failed before this point, and there
>> was already one "goto err" above this code and I added another to
>> properly handle not allocating the led name.  If it failed there it
>> would leave an LED lying around but free the memory underneath it.  So
>> instead, modify the failure recovery code to be priv->num_leds-1 instead
>> of priv->num_leds-2 and don't increment priv->num_leds until you have
>> success.
>>
>>>>                                       dev, NULL);
>>>>                 if (ret < 0) {
>>>>                         fwnode_handle_put(child);
>>>>                         goto err;
>>>>                 }
>>>> +               priv->num_leds++;
>>> Why need this?
>> See above.
>>
>>>>         }
>>>>
>>>>         return priv;
>>>>
>>>>  err:
>>>> -       for (count = priv->num_leds - 2; count >= 0; count--)
>>>> +       for (count = priv->num_leds - 1; count >= 0; count--)
>>>>                 delete_gpio_led(&priv->leds[count]);
>>>> +       devm_kfree(dev, priv);
>>> priv is created by devm_kzalloc(), so if driver probing return error,
>>> it will be freed automatically, you don't need call devm_free();
>> Ah, ok.  Then this is unnecessary.  Do want a new patch?
>>
> I see, please provide a new patch. I'm going to merge this fix soon.
>
> Thanks,
> -Bryan
>
>
>> Thanks,
>>
>> -corey
>>
>>>>         return ERR_PTR(ret);
>>>>  }
>>>>
>>>> @@ -283,6 +287,7 @@ static int gpio_led_remove(struct platform_device *pdev)
>>>>
>>>>         for (i = 0; i < priv->num_leds; i++)
>>>>                 delete_gpio_led(&priv->leds[i]);
>>>> +       devm_kfree(&pdev->dev, priv);
>>> No need this during remove.
>>>
>>>>         return 0;
>>>>  }
>>>> --
>>>> 1.8.3.1
>>>>
>>>> --
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