linux-kernel - Re: [PATCH] gpiolib: free device name on error path to fix kmemleak

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Message-ID: <CAHp75VemJWQDKFFrrCKWnUGHFiPhuh=4Aqhn8T6qF5yuMOCOKg@mail.gmail.com>
Date:   Fri, 29 Jan 2021 19:26:21 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     quanyang.wang@...driver.com
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpiolib: free device name on error path to fix kmemleak

On Fri, Jan 29, 2021 at 2:01 PM <quanyang.wang@...driver.com> wrote:
>
> From: Quanyang Wang <quanyang.wang@...driver.com>
>
> In gpiochip_add_data_with_key, we should check the return value of
> dev_set_name to ensure that device name is allocated successfully
> and then add a label on the error path to free device name to fix
> kmemleak as below:

Thanks for the report.
Unfortunately...

> +       ret = dev_set_name(&gdev->dev, GPIOCHIP_NAME "%d", gdev->id);
> +       if (ret)
> +               goto err_free_ida;

...

> +err_free_dev_name:
> +       kfree(dev_name(&gdev->dev));

...this approach seems to  create a possible double free if I'm not mistaken.

The idea is that device name should be cleaned in kobject ->release()
callback when device is put.

Can you elaborate?

-- 
With Best Regards,
Andy Shevchenko