Patch "gpiolib: Fix unaligned used of reference counters" has been added to the 4.6-stable tree

Patch "gpiolib: Fix unaligned used of reference counters" has been added to the 4.6-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    gpiolib: Fix unaligned used of reference counters

to the 4.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     gpiolib-fix-unaligned-used-of-reference-counters.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From f4833b8cc7edab57d3f3033e549111a546c2e02b Mon Sep 17 00:00:00 2001
From: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Date: Fri, 3 Jun 2016 19:10:02 +0200
Subject: gpiolib: Fix unaligned used of reference counters

From: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>

commit f4833b8cc7edab57d3f3033e549111a546c2e02b upstream.

gpiolib relies on the reference counters to clean up the gpio_device
structure.

Although the number of get/put is properly aligned on gpiolib.c
itself, it does not take into consideration how the referece counters
are affected by other external functions such as cdev_add and device_add.

Because of this, after the last call to put_device, the reference counter
has a value of +3, therefore never calling gpiodevice_release.

Due to the fact that some of the device  has already been cleaned on
gpiochip_remove, the library will end up OOPsing the kernel (e.g. a call
to of_gpiochip_find_and_xlate).

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpio/gpiolib.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -438,7 +438,6 @@ static void gpiodevice_release(struct de
 {
 	struct gpio_device *gdev = dev_get_drvdata(dev);
 
-	cdev_del(&gdev->chrdev);
 	list_del(&gdev->list);
 	ida_simple_remove(&gpio_ida, gdev->id);
 	kfree(gdev->label);
@@ -471,7 +470,6 @@ static int gpiochip_setup_dev(struct gpi
 
 	/* From this point, the .release() function cleans up gpio_device */
 	gdev->dev.release = gpiodevice_release;
-	get_device(&gdev->dev);
 	pr_debug("%s: registered GPIOs %d to %d on device: %s (%s)\n",
 		 __func__, gdev->base, gdev->base + gdev->ngpio - 1,
 		 dev_name(&gdev->dev), gdev->chip->label ? : "generic");
@@ -742,6 +740,8 @@ void gpiochip_remove(struct gpio_chip *c
 	 * be removed, else it will be dangling until the last user is
 	 * gone.
 	 */
+	cdev_del(&gdev->chrdev);
+	device_del(&gdev->dev);
 	put_device(&gdev->dev);
 }
 EXPORT_SYMBOL_GPL(gpiochip_remove);


Patches currently in stable-queue which might be from ricardo.ribalda@gmail.com are

queue-4.6/gpiolib-fix-unaligned-used-of-reference-counters.patch
queue-4.6/gpiolib-fix-null-pointer-deference.patch