linux-kernel - Re: [PATCH 1/2] gpiolib: irqchip: prevent driver unloading if gpio is used as irq only

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Date:	Tue, 30 Jun 2015 22:47:51 +0900
From:	Alexandre Courbot <gnurou@...il.com>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Sekhar Nori <nsekhar@...com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Johan Hovold <johan@...nel.org>
Subject: Re: [PATCH 1/2] gpiolib: irqchip: prevent driver unloading if gpio is
 used as irq only

On Fri, Jun 26, 2015 at 2:30 AM, Grygorii Strashko
<grygorii.strashko@...com> wrote:
> Now nothing prevents GPIO driver from being unloaded if its gpios
> were requested as GPIO IRQs only (without calling gpio_request()).
>
> Hence, add calls of try_module_get()/module_put() into
> gpiochip_irq_reqres/relres() to track such scenario properly.

Bad things could happen indeed.

Reviewed-by: Alexandre Courbot <acourbot@...dia.com>

>
> Cc: Johan Hovold <johan@...nel.org>
> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
> ---
>  drivers/gpio/gpiolib.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index be42ab3..9b1d247 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -522,10 +522,14 @@ static int gpiochip_irq_reqres(struct irq_data *d)
>  {
>         struct gpio_chip *chip = irq_data_get_irq_chip_data(d);
>
> +       if (!try_module_get(chip->owner))
> +               return -ENODEV;
> +
>         if (gpiochip_lock_as_irq(chip, d->hwirq)) {
>                 chip_err(chip,
>                         "unable to lock HW IRQ %lu for IRQ\n",
>                         d->hwirq);
> +               module_put(chip->owner);
>                 return -EINVAL;
>         }
>         return 0;
> @@ -536,6 +540,7 @@ static void gpiochip_irq_relres(struct irq_data *d)
>         struct gpio_chip *chip = irq_data_get_irq_chip_data(d);
>
>         gpiochip_unlock_as_irq(chip, d->hwirq);
> +       module_put(chip->owner);
>  }
>
>  static int gpiochip_to_irq(struct gpio_chip *chip, unsigned offset)
> --
> 2.4.4
>
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