[PATCH 1/2] gpio: fix NULL-deref-on-deregistration regression

From: Johan Hovold <johan@kernel.org>
To: Linus Walleij <linus.walleij@linaro.org>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Saravana Kannan <saravanak@google.com>,
	linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org,
	Johan Hovold <johan@kernel.org>,
	syzbot+d27b4c8adbbff70fbfde@syzkaller.appspotmail.com
Subject: [PATCH 1/2] gpio: fix NULL-deref-on-deregistration regression
Date: Fri, 26 Feb 2021 15:52:45 +0100	[thread overview]
Message-ID: <20210226145246.1171-2-johan@kernel.org> (raw)
In-Reply-To: <20210226145246.1171-1-johan@kernel.org>

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 <saravanak@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reported-by: syzbot+d27b4c8adbbff70fbfde@syzkaller.appspotmail.com
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 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

