Commit 81570d6a authored by Bartosz Golaszewski's avatar Bartosz Golaszewski
Browse files

gpiolib: protect gpio_chip with SRCU in array_info paths in multi get/set 

During the locking rework in GPIOLIB, we omitted one important use-case,
namely: setting and getting values for GPIO descriptor arrays with
array_info present.

This patch does two things: first it makes struct gpio_array store the
address of the underlying GPIO device and not chip. Next: it protects
the chip with SRCU from removal in gpiod_get_array_value_complex() and
gpiod_set_array_value_complex().

Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250215095655.23152-1-brgl@bgdev.pl


Signed-off-by: default avatarBartosz Golaszewski <bartosz.golaszewski@linaro.org>
parent 4e667a19

drivers/gpio/gpiolib.c

+33 −15
Original line number Diff line number Diff line
@@ -3143,6 +3143,8 @@ static int gpiod_get_raw_value_commit(const struct gpio_desc *desc) 
static int gpio_chip_get_multiple(struct gpio_chip *gc,

				  unsigned long *mask, unsigned long *bits)

{

	lockdep_assert_held(&gc->gpiodev->srcu);



	if (gc->get_multiple)

		return gc->get_multiple(gc, mask, bits);

	if (gc->get) {
@@ -3173,6 +3175,7 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep, 
				  struct gpio_array *array_info,

				  unsigned long *value_bitmap)

{

	struct gpio_chip *gc;

	int ret, i = 0;



	/*
@@ -3184,10 +3187,15 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep, 
	    array_size <= array_info->size &&

	    (void *)array_info == desc_array + array_info->size) {

		if (!can_sleep)

			WARN_ON(array_info->chip->can_sleep);

			WARN_ON(array_info->gdev->can_sleep);



		ret = gpio_chip_get_multiple(array_info->chip,

					     array_info->get_mask,

		guard(srcu)(&array_info->gdev->srcu);

		gc = srcu_dereference(array_info->gdev->chip,

				      &array_info->gdev->srcu);

		if (!gc)

			return -ENODEV;



		ret = gpio_chip_get_multiple(gc, array_info->get_mask,

					     value_bitmap);

		if (ret)

			return ret;
@@ -3468,6 +3476,8 @@ static void gpiod_set_raw_value_commit(struct gpio_desc *desc, bool value) 
static void gpio_chip_set_multiple(struct gpio_chip *gc,

				   unsigned long *mask, unsigned long *bits)

{

	lockdep_assert_held(&gc->gpiodev->srcu);



	if (gc->set_multiple) {

		gc->set_multiple(gc, mask, bits);

	} else {
@@ -3485,6 +3495,7 @@ int gpiod_set_array_value_complex(bool raw, bool can_sleep, 
				  struct gpio_array *array_info,

				  unsigned long *value_bitmap)

{

	struct gpio_chip *gc;

	int i = 0;



	/*
@@ -3496,14 +3507,19 @@ int gpiod_set_array_value_complex(bool raw, bool can_sleep, 
	    array_size <= array_info->size &&

	    (void *)array_info == desc_array + array_info->size) {

		if (!can_sleep)

			WARN_ON(array_info->chip->can_sleep);

			WARN_ON(array_info->gdev->can_sleep);



		guard(srcu)(&array_info->gdev->srcu);

		gc = srcu_dereference(array_info->gdev->chip,

				      &array_info->gdev->srcu);

		if (!gc)

			return -ENODEV;



		if (!raw && !bitmap_empty(array_info->invert_mask, array_size))

			bitmap_xor(value_bitmap, value_bitmap,

				   array_info->invert_mask, array_size);



		gpio_chip_set_multiple(array_info->chip, array_info->set_mask,

				       value_bitmap);

		gpio_chip_set_multiple(gc, array_info->set_mask, value_bitmap);



		i = find_first_zero_bit(array_info->set_mask, array_size);

		if (i == array_size)
@@ -4765,9 +4781,10 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev, 
{

	struct gpio_desc *desc;

	struct gpio_descs *descs;

	struct gpio_device *gdev;

	struct gpio_array *array_info = NULL;

	struct gpio_chip *gc;

	int count, bitmap_size;

	unsigned long dflags;

	size_t descs_size;



	count = gpiod_count(dev, con_id);
@@ -4788,7 +4805,7 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev, 


		descs->desc[descs->ndescs] = desc;



		gc = gpiod_to_chip(desc);

		gdev = gpiod_to_gpio_device(desc);

		/*

		 * If pin hardware number of array member 0 is also 0, select

		 * its chip as a candidate for fast bitmap processing path.
@@ -4796,8 +4813,8 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev, 
		if (descs->ndescs == 0 && gpio_chip_hwgpio(desc) == 0) {

			struct gpio_descs *array;



			bitmap_size = BITS_TO_LONGS(gc->ngpio > count ?

						    gc->ngpio : count);

			bitmap_size = BITS_TO_LONGS(gdev->ngpio > count ?

						    gdev->ngpio : count);



			array = krealloc(descs, descs_size +

					 struct_size(array_info, invert_mask, 3 * bitmap_size),
@@ -4817,7 +4834,7 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev, 


			array_info->desc = descs->desc;

			array_info->size = count;

			array_info->chip = gc;

			array_info->gdev = gdev;

			bitmap_set(array_info->get_mask, descs->ndescs,

				   count - descs->ndescs);

			bitmap_set(array_info->set_mask, descs->ndescs,
@@ -4830,7 +4847,7 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev, 
			continue;



		/* Unmark array members which don't belong to the 'fast' chip */

		if (array_info->chip != gc) {

		if (array_info->gdev != gdev) {

			__clear_bit(descs->ndescs, array_info->get_mask);

			__clear_bit(descs->ndescs, array_info->set_mask);

		}
@@ -4853,9 +4870,10 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev, 
					    array_info->set_mask);

			}

		} else {

			dflags = READ_ONCE(desc->flags);

			/* Exclude open drain or open source from fast output */

			if (gpiochip_line_is_open_drain(gc, descs->ndescs) ||

			    gpiochip_line_is_open_source(gc, descs->ndescs))

			if (test_bit(FLAG_OPEN_DRAIN, &dflags) ||

			    test_bit(FLAG_OPEN_SOURCE, &dflags))

				__clear_bit(descs->ndescs,

					    array_info->set_mask);

			/* Identify 'fast' pins which require invertion */
@@ -4867,7 +4885,7 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev, 
	if (array_info)

		dev_dbg(dev,

			"GPIO array info: chip=%s, size=%d, get_mask=%lx, set_mask=%lx, invert_mask=%lx\n",

			array_info->chip->label, array_info->size,

			array_info->gdev->label, array_info->size,

			*array_info->get_mask, *array_info->set_mask,

			*array_info->invert_mask);

	return descs;

drivers/gpio/gpiolib.h

+2 −2
Original line number Diff line number Diff line
@@ -114,7 +114,7 @@ extern const char *const gpio_suffixes[]; 
 *

 * @desc:		Array of pointers to the GPIO descriptors

 * @size:		Number of elements in desc

 * @chip:		Parent GPIO chip

 * @gdev:		Parent GPIO device

 * @get_mask:		Get mask used in fastpath

 * @set_mask:		Set mask used in fastpath

 * @invert_mask:	Invert mask used in fastpath
@@ -126,7 +126,7 @@ extern const char *const gpio_suffixes[]; 
struct gpio_array {

	struct gpio_desc	**desc;

	unsigned int		size;

	struct gpio_chip	*chip;

	struct gpio_device	*gdev;

	unsigned long		*get_mask;

	unsigned long		*set_mask;

	unsigned long		invert_mask[];