FAILED: patch "[PATCH] gpio: sysfs: fix memory leaks and device hotplug" failed to apply to 3.10-stable tree

FAILED: patch "[PATCH] gpio: sysfs: fix memory leaks and device hotplug" failed to apply to 3.10-stable tree

[gregkh]

The patch below does not apply to the 3.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 483d821108791092798f5d230686868112927044 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Tue, 21 Apr 2015 17:42:09 +0200
Subject: [PATCH] gpio: sysfs: fix memory leaks and device hotplug

Unregister GPIOs requested through sysfs at chip remove to avoid leaking
the associated memory and sysfs entries.

The stale sysfs entries prevented the gpio numbers from being exported
when the gpio range was later reused (e.g. at device reconnect).

This also fixes the related module-reference leak.

Note that kernfs makes sure that any on-going sysfs operations finish
before the class devices are unregistered and that further accesses
fail.

The chip exported flag is used to prevent gpiod exports during removal.
This also makes it harder to trigger, but does not fix, the related race
between gpiochip_remove and export_store, which is really a race with
gpiod_request that needs to be addressed separately.

Also note that this would prevent the crashes (e.g. NULL-dereferences)
at reconnect that affects pre-3.18 kernels, as well as use-after-free on
operations on open attribute files on pre-3.14 kernels (prior to
kernfs).

Fixes: d8f388d8dc8d ("gpio: sysfs interface")
Cc: stable <stable@vger.kernel.org>	# v2.6.27: 01cca93a9491
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 7722ed53bd65..af3bc7a8033b 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -551,6 +551,7 @@ static struct class gpio_class = {
  */
 int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 {
+	struct gpio_chip	*chip;
 	unsigned long		flags;
 	int			status;
 	const char		*ioname = NULL;
@@ -568,8 +569,16 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 		return -EINVAL;
 	}
 
+	chip = desc->chip;
+
 	mutex_lock(&sysfs_lock);
 
+	/* check if chip is being removed */
+	if (!chip || !chip->exported) {
+		status = -ENODEV;
+		goto fail_unlock;
+	}
+
 	spin_lock_irqsave(&gpio_lock, flags);
 	if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
 	     test_bit(FLAG_EXPORT, &desc->flags)) {
@@ -783,12 +792,15 @@ void gpiochip_unexport(struct gpio_chip *chip)
 {
 	int			status;
 	struct device		*dev;
+	struct gpio_desc *desc;
+	unsigned int i;
 
 	mutex_lock(&sysfs_lock);
 	dev = class_find_device(&gpio_class, NULL, chip, match_export);
 	if (dev) {
 		put_device(dev);
 		device_unregister(dev);
+		/* prevent further gpiod exports */
 		chip->exported = false;
 		status = 0;
 	} else
@@ -797,6 +809,13 @@ void gpiochip_unexport(struct gpio_chip *chip)
 
 	if (status)
 		chip_dbg(chip, "%s: status %d\n", __func__, status);
+
+	/* unregister gpiod class devices owned by sysfs */
+	for (i = 0; i < chip->ngpio; i++) {
+		desc = &chip->desc[i];
+		if (test_and_clear_bit(FLAG_SYSFS, &desc->flags))
+			gpiod_free(desc);
+	}
 }
 
 static int __init gpiolib_sysfs_init(void)

Re: FAILED: patch "[PATCH] gpio: sysfs: fix memory leaks and device hotplug" failed to apply to 3.10-stable tree

[Johan Hovold]

On Thu, May 14, 2015 at 06:53:49PM -0700, Greg Kroah-Hartman wrote:
> 
> The patch below does not apply to the 3.10-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.

This patch depends commit 01cca93a9491 ("gpio: unregister gpiochip
device before removing it") which needs to be backported as well.

I'll respond to this message with a tested backport of both patches.

Thanks,
Johan

[PATCH-3.10 1/2] gpio: unregister gpiochip device before removing it

[Johan Hovold]

commit 01cca93a9491ed95992523ff7e79dd9bfcdea8e0 upstream.

Unregister gpiochip device (used to export information through sysfs)
before removing it internally. This way removal will reverse addition.

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/gpio/gpiolib.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index ca1cb2d756c2..df4780810e83 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1265,6 +1265,8 @@ int gpiochip_remove(struct gpio_chip *chip)
 	int		status = 0;
 	unsigned	id;
 
+	gpiochip_unexport(chip);
+
 	spin_lock_irqsave(&gpio_lock, flags);
 
 	gpiochip_remove_pin_ranges(chip);
@@ -1285,9 +1287,6 @@ int gpiochip_remove(struct gpio_chip *chip)
 
 	spin_unlock_irqrestore(&gpio_lock, flags);
 
-	if (status == 0)
-		gpiochip_unexport(chip);
-
 	return status;
 }
 EXPORT_SYMBOL_GPL(gpiochip_remove);
-- 
2.3.6

[PATCH-3.10 2/2] gpio: sysfs: fix memory leaks and device hotplug

[Johan Hovold]

commit 483d821108791092798f5d230686868112927044 upstream.

Unregister GPIOs requested through sysfs at chip remove to avoid leaking
the associated memory and sysfs entries.

The stale sysfs entries prevented the gpio numbers from being exported
when the gpio range was later reused (e.g. at device reconnect).

This also fixes the related module-reference leak.

Note that kernfs makes sure that any on-going sysfs operations finish
before the class devices are unregistered and that further accesses
fail.

The chip exported flag is used to prevent gpiod exports during removal.
This also makes it harder to trigger, but does not fix, the related race
between gpiochip_remove and export_store, which is really a race with
gpiod_request that needs to be addressed separately.

Also note that this would prevent the crashes (e.g. NULL-dereferences)
at reconnect that affects pre-3.18 kernels, as well as use-after-free on
operations on open attribute files on pre-3.14 kernels (prior to
kernfs).

Fixes: d8f388d8dc8d ("gpio: sysfs interface")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/gpio/gpiolib.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index df4780810e83..c3768fafff45 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -752,6 +752,7 @@ static struct class gpio_class = {
  */
 static int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 {
+	struct gpio_chip	*chip;
 	unsigned long		flags;
 	int			status;
 	const char		*ioname = NULL;
@@ -769,8 +770,16 @@ static int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 		return -EINVAL;
 	}
 
+	chip = desc->chip;
+
 	mutex_lock(&sysfs_lock);
 
+	/* check if chip is being removed */
+	if (!chip || !chip->exported) {
+		status = -ENODEV;
+		goto fail_unlock;
+	}
+
 	spin_lock_irqsave(&gpio_lock, flags);
 	if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
 	     test_bit(FLAG_EXPORT, &desc->flags)) {
@@ -1040,6 +1049,8 @@ static void gpiochip_unexport(struct gpio_chip *chip)
 {
 	int			status;
 	struct device		*dev;
+	struct gpio_desc *desc;
+	unsigned int i;
 
 	mutex_lock(&sysfs_lock);
 	dev = class_find_device(&gpio_class, NULL, chip, match_export);
@@ -1047,6 +1058,7 @@ static void gpiochip_unexport(struct gpio_chip *chip)
 		sysfs_remove_group(&dev->kobj, &gpiochip_attr_group);
 		put_device(dev);
 		device_unregister(dev);
+		/* prevent further gpiod exports */
 		chip->exported = 0;
 		status = 0;
 	} else
@@ -1056,6 +1068,13 @@ static void gpiochip_unexport(struct gpio_chip *chip)
 	if (status)
 		pr_debug("%s: chip %s status %d\n", __func__,
 				chip->label, status);
+
+	/* unregister gpiod class devices owned by sysfs */
+	for (i = 0; i < chip->ngpio; i++) {
+		desc = &chip->desc[i];
+		if (test_and_clear_bit(FLAG_SYSFS, &desc->flags))
+			gpiod_free(desc);
+	}
 }
 
 static int __init gpiolib_sysfs_init(void)
-- 
2.3.6