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From:   Bartosz Golaszewski <bgolaszewski@baylibre.com>
Date:   Mon, 7 Dec 2020 10:51:20 +0100
Message-ID: <CAMpxmJVd7NrCQMq99iGLj7BsKooK0B5qNz3iEE=sPri90zdEAw@mail.gmail.com>
Subject: Re: [PATCH] rtc: fix RTC removal
To:     Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc:     Alessandro Zummo <a.zummo@towertech.it>, linux-rtc@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>
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On Sun, Dec 6, 2020 at 12:14 AM Alexandre Belloni
<alexandre.belloni@bootlin.com> wrote:
>
> Since the rtc_register_device, removing an RTC device will end with a
> refcount_t: underflow; use-after-free warning since put_device is called
> twice in the device tear down path.
>
> Fixes: fdcfd854333b ("rtc: rework rtc_register_device() resource management")
> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
> ---
>  drivers/rtc/class.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
> index e6b44b7c4ad3..5c6748dfa55d 100644
> --- a/drivers/rtc/class.c
> +++ b/drivers/rtc/class.c
> @@ -335,7 +335,6 @@ static void devm_rtc_unregister_device(void *data)
>         cdev_device_del(&rtc->char_dev, &rtc->dev);
>         rtc->ops = NULL;
>         mutex_unlock(&rtc->ops_lock);
> -       put_device(&rtc->dev);
>  }
>
>  static void devm_rtc_release_device(void *res)
> --
> 2.28.0
>

Eek! Thanks for fixing that.

Reviewed-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>