diff mbox series

[v2,1/3] gpiolib: remove the GPIO device from the list when it's unregistered

Message ID 20240102155949.73434-2-brgl@bgdev.pl
State New
Headers show
Series gpiolib: use a read-write semaphore to protect the GPIO device list | expand

Commit Message

Bartosz Golaszewski Jan. 2, 2024, 3:59 p.m. UTC 
From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

If we wait until the GPIO device's .release() callback gets invoked
before we remove it from the global device list, then we risk that
someone will look it up using gpio_device_find() between where we
dropped the last reference and before .release() is done taking a
reference again to an object that's being released.

The device must be removed when it's being unregistered - just like how
we remove it from the GPIO bus.

Fixes: ff2b13592299 ("gpio: make the gpiochip a real device")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/gpio/gpiolib.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Comments

Linus Walleij Jan. 2, 2024, 10:11 p.m. UTC | #1 
On Tue, Jan 2, 2024 at 4:59 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:

> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>
> If we wait until the GPIO device's .release() callback gets invoked
> before we remove it from the global device list, then we risk that
> someone will look it up using gpio_device_find() between where we
> dropped the last reference and before .release() is done taking a
> reference again to an object that's being released.
>
> The device must be removed when it's being unregistered - just like how
> we remove it from the GPIO bus.
>
> Fixes: ff2b13592299 ("gpio: make the gpiochip a real device")
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Makes sense!
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij
diff mbox series

Patch

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index e21497b989a1..e019c4243809 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -651,9 +651,6 @@  static void gpiodev_release(struct device *dev)
 {
 	struct gpio_device *gdev = to_gpio_device(dev);
 
-	scoped_guard(mutex, &gpio_devices_lock)
-		list_del(&gdev->list);
-
 	ida_free(&gpio_ida, gdev->id);
 	kfree_const(gdev->label);
 	kfree(gdev->descs);
@@ -1068,6 +1065,9 @@  void gpiochip_remove(struct gpio_chip *gc)
 		dev_crit(&gdev->dev,
 			 "REMOVING GPIOCHIP WITH GPIOS STILL REQUESTED\n");
 
+	scoped_guard(mutex, &gpio_devices_lock)
+		list_del(&gdev->list);
+
 	/*
 	 * The gpiochip side puts its use of the device to rest here:
 	 * if there are no userspace clients, the chardev and device will