linux-kernel - Re: [PATCH v3] leds: Introduce userspace leds driver

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Date:   Fri, 16 Sep 2016 10:18:22 -0500
From:   David Lechner <david@...hnology.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Jacek Anaszewski <j.anaszewski@...sung.com>,
        Richard Purdie <rpurdie@...ys.net>,
        linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org,
        Marcel Holtmann <marcel@...tmann.org>
Subject: Re: [PATCH v3] leds: Introduce userspace leds driver

On 09/16/2016 12:51 AM, Pavel Machek wrote:
> On Thu 2016-09-15 10:31:50, David Lechner wrote:
>> On 09/15/2016 09:54 AM, Jacek Anaszewski wrote:
>>> Hi Pavel,
>>>
>>> On 09/15/2016 03:08 PM, Pavel Machek wrote:
>>>> Hi!
>>>>
>>>>>> +    if (copy_from_user(&udev->user_dev, buffer,
>>>>>> +               sizeof(struct uleds_user_dev))) {
>>>>>> +        ret = -EFAULT;
>>>>>> +        goto out;
>>>>>> +    }
>>>>>> +
>>>>>> +    if (!udev->user_dev.name[0]) {
>>>>>> +        ret = -EINVAL;
>>>>>> +        goto out;
>>>>>> +    }
>>>>>> +
>>>>>> +    ret = led_classdev_register(NULL, &udev->led_cdev);
>>>>>> +    if (ret < 0)
>>>>>> +        goto out;
>>>>
>>>> No sanity checking on the name -> probably a security hole. Do not
>>>> push this upstream before this is fixed.
>>>
>>> Thanks for catching this.
>>>
>>> David, please check if the LED name sticks to the LED class
>>> device naming convention.
>>
>> I don't think it is a good idea to enforce the LED class naming convention.
>> Someone may have a userspace application they want to test that has a
>> hard-coded name that does not follow the convention.
>
> Umm.
>
> Noone has applications with hardcoded names that are not possible
> today, right?
>
> And better not encourage crazy names.
>
> Best regards,
> 									Pavel
>

Here is the actual `ls /sys/class/leds` from my Raspberry Pi:

led0                      pistorms:BA:red:ev3dev    pistorms:BB:red:ev3dev
pistorms:BA:blue:ev3dev   pistorms:BB:blue:ev3dev
pistorms:BA:green:ev3dev  pistorms:BB:green:ev3dev



Suppose I want to use uleds on my desktop to simulate my Raspberry Pi. 
If we restrict the name to the LEDs class convention of 
device:color:function, then I can't do this. led0 does not follow the 
convention at all. The other do follow the convention, but only if we 
allow that the device portion of the name can also include ':'.

It's too late, the crazy names already exist.