[PATCH v2 2/2] gpio: fix gpio-device list corruption

[PATCH v2 2/2] gpio: fix gpio-device list corruption

[Johan Hovold]

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@vger.kernel.org      # 4.6
Reviewed-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/gpio/gpiolib.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 6e0572515d02..4253837f870b 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);
+
 	ida_free(&gpio_ida, gdev->id);
 	kfree_const(gdev->label);
 	kfree(gdev->descs);
-- 
2.26.2

Re: [PATCH v2 2/2] gpio: fix gpio-device list corruption

[Linus Walleij]

On Mon, Mar 1, 2021 at 10:05 AM Johan Hovold <johan@kernel.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@vger.kernel.org      # 4.6
> Reviewed-by: Saravana Kannan <saravanak@google.com>
> Signed-off-by: Johan Hovold <johan@kernel.org>

Excellent fix as well,
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij