Re: [PATCH v3 01/11] leds: led-class: Add missing put_device() to led_put()

From: Hans de Goede <hdegoede@redhat.com>
To: Andy Shevchenko <andy@kernel.org>
Cc: Mark Gross <markgross@kernel.org>, Pavel Machek <pavel@ucw.cz>,
	Lee Jones <lee@kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Daniel Scally <djrscally@gmail.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	platform-driver-x86@vger.kernel.org, linux-leds@vger.kernel.org,
	linux-gpio@vger.kernel.org, Kate Hsuan <hpa@redhat.com>,
	Mark Pearson <markpearson@lenovo.com>,
	Andy Yeh <andy.yeh@intel.com>, Yao Hao <yao.hao@intel.com>,
	linux-media@vger.kernel.org
Subject: Re: [PATCH v3 01/11] leds: led-class: Add missing put_device() to led_put()
Date: Fri, 16 Dec 2022 16:22:05 +0100	[thread overview]
Message-ID: <1f784f94-cbb1-79db-3796-ec5c21c9e8e2@redhat.com> (raw)
In-Reply-To: <Y5x4z6N5ZjdomP4c@smile.fi.intel.com>

Hi,

On 12/16/22 14:55, Andy Shevchenko wrote:
> On Fri, Dec 16, 2022 at 03:35:29PM +0200, Andy Shevchenko wrote:
>> On Fri, Dec 16, 2022 at 12:30:03PM +0100, Hans de Goede wrote:
> 
> ...
> 
>>>  	led_cdev = dev_get_drvdata(led_dev);
>>>  
>>> -	if (!try_module_get(led_cdev->dev->parent->driver->owner))
>>> +	if (!try_module_get(led_cdev->dev->parent->driver->owner)) {
>>> +		put_device(led_cdev->dev);
>>>  		return ERR_PTR(-ENODEV);
>>> +	}
>>>  
>>>  	return led_cdev;
>>
>> ...
>>
>>>  void led_put(struct led_classdev *led_cdev)
>>>  {
>>>  	module_put(led_cdev->dev->parent->driver->owner);
>>> +	put_device(led_cdev->dev);
>>
>> Hmm... It was in the original submission.
>>
>> https://lore.kernel.org/linux-leds/1443605522-1118-2-git-send-email-tomi.valkeinen@ti.com/
> 
> ...
> 
>> Nevertheless, shouldn't you put device before putting module? (It may need to
>> save the owner of the driver, I think.)
> 
> I think this is wrong, the symmetry is kept correct in your patch.

Right, the line above dereferences led_cdev->dev, so the put()
must be done after that line.

Regards,

Hans