Fix a NULL-pointer deference when deregistering the gpio character
device that was introduced by the recent stub-driver hack. When the new
"driver" is unbound as part of deregistration, driver core clears the
driver-data pointer which is used to retrieve the struct gpio_device in
its release callback.

Fix this by using container_of() in the release callback as should have
been done all along.

Fixes: 4731210c09f5 ("gpiolib: Bind gpio_device to a driver to enable 
fw_devlink=on by default")
Cc: Saravana Kannan <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Reported-by: [email protected]
Signed-off-by: Johan Hovold <[email protected]>
---
 drivers/gpio/gpiolib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index adf55db080d8..e1016bc8cf14 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -474,7 +474,7 @@ EXPORT_SYMBOL_GPL(gpiochip_line_is_valid);
 
 static void gpiodevice_release(struct device *dev)
 {
-       struct gpio_device *gdev = dev_get_drvdata(dev);
+       struct gpio_device *gdev = container_of(dev, struct gpio_device, dev);
 
        list_del(&gdev->list);
        ida_free(&gpio_ida, gdev->id);
-- 
2.26.2

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