linux-kernel - Re: [PATCH 2/2] gpio: fix gpio-device list corruption

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Date:   Fri, 26 Feb 2021 12:59:17 -0800
From:   Saravana Kannan <saravanak@...gle.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH 2/2] gpio: fix gpio-device list corruption

On Fri, Feb 26, 2021 at 6:55 AM Johan Hovold <johan@...nel.org> wrote:
>
> Make sure to hold the gpio_lock when removing the gpio device from the
> gpio_devices list (when dropping the last reference) to avoid corrupting
> the list when there are concurrent accesses.
>
> Fixes: ff2b13592299 ("gpio: make the gpiochip a real device")
> Cc: stable@...r.kernel.org      # 4.6
> Signed-off-by: Johan Hovold <johan@...nel.org>
> ---
>  drivers/gpio/gpiolib.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index e1016bc8cf14..42bdc55a15f9 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -475,8 +475,12 @@ EXPORT_SYMBOL_GPL(gpiochip_line_is_valid);
>  static void gpiodevice_release(struct device *dev)
>  {
>         struct gpio_device *gdev = container_of(dev, struct gpio_device, dev);
> +       unsigned long flags;
>
> +       spin_lock_irqsave(&gpio_lock, flags);
>         list_del(&gdev->list);
> +       spin_unlock_irqrestore(&gpio_lock, flags);
> +

Reviewed-by: Saravana Kannan <saravanak@...gle.com>

-Saravana

>         ida_free(&gpio_ida, gdev->id);
>         kfree_const(gdev->label);
>         kfree(gdev->descs);
> --
> 2.26.2
>