[PATCH v3 1/8] gpiolib: fix GPIO descriptor leak in gpiod_get_array()

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

In gpiod_get_array(), descs->ndescs is used as the loop induction
variable and is only incremented at the end of each iteration. When
krealloc() fails on the first iteration (when index is 0),
descs->desc[0] has already been acquired via gpiod_get_index(), but
descs->ndescs is still 0. Consequently, gpiod_put_array() frees descs
without releasing descs->desc[0], leaking the descriptor.

Fix this by using a dedicated loop induction variable and incrementing
descs->ndescs immediately upon storing the retrieved descriptor.
Additionally, since the fast-path array_info setup only executes for the
first element (index 0), simplify the bitmap_set() calls to start at bit
0 for count bits instead of calculating offsets from the loop index.

Fixes: bf9346f5d47b ("gpiolib: Identify arrays matching GPIO hardware")
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/gpio/gpiolib.c | 34 ++++++++++++++--------------------
 1 file changed, 14 insertions(+), 20 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index fbdeda2f2787..a5a519c0f001 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -5243,21 +5243,21 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
 	if (!descs)
 		return ERR_PTR(-ENOMEM);
 
-	for (descs->ndescs = 0; descs->ndescs < count; descs->ndescs++) {
-		desc = gpiod_get_index(dev, con_id, descs->ndescs, flags);
+	for (int i = 0; i < count; i++) {
+		desc = gpiod_get_index(dev, con_id, i, flags);
 		if (IS_ERR(desc)) {
 			gpiod_put_array(descs);
 			return ERR_CAST(desc);
 		}
 
-		descs->desc[descs->ndescs] = desc;
+		descs->desc[descs->ndescs++] = 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.
 		 */
-		if (descs->ndescs == 0 && gpiod_hwgpio(desc) == 0) {
+		if (i == 0 && gpiod_hwgpio(desc) == 0) {
 			struct gpio_descs *array;
 
 			bitmap_size = BITS_TO_LONGS(gdev->ngpio > count ?
@@ -5282,10 +5282,8 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
 			array_info->desc = descs->desc;
 			array_info->size = count;
 			array_info->gdev = gdev;
-			bitmap_set(array_info->get_mask, descs->ndescs,
-				   count - descs->ndescs);
-			bitmap_set(array_info->set_mask, descs->ndescs,
-				   count - descs->ndescs);
+			bitmap_set(array_info->get_mask, 0, count);
+			bitmap_set(array_info->set_mask, 0, count);
 			descs->info = array_info;
 		}
 
@@ -5295,38 +5293,34 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
 
 		/* Unmark array members which don't belong to the 'fast' chip */
 		if (array_info->gdev != gdev) {
-			__clear_bit(descs->ndescs, array_info->get_mask);
-			__clear_bit(descs->ndescs, array_info->set_mask);
+			__clear_bit(i, array_info->get_mask);
+			__clear_bit(i, array_info->set_mask);
 		}
 		/*
 		 * Detect array members which belong to the 'fast' chip
 		 * but their pins are not in hardware order.
 		 */
-		else if (gpiod_hwgpio(desc) != descs->ndescs) {
+		else if (gpiod_hwgpio(desc) != i) {
 			/*
 			 * Don't use fast path if all array members processed so
 			 * far belong to the same chip as this one but its pin
 			 * hardware number is different from its array index.
 			 */
-			if (bitmap_full(array_info->get_mask, descs->ndescs)) {
+			if (bitmap_full(array_info->get_mask, i)) {
 				array_info = NULL;
 			} else {
-				__clear_bit(descs->ndescs,
-					    array_info->get_mask);
-				__clear_bit(descs->ndescs,
-					    array_info->set_mask);
+				__clear_bit(i, array_info->get_mask);
+				__clear_bit(i, array_info->set_mask);
 			}
 		} else {
 			dflags = READ_ONCE(desc->flags);
 			/* Exclude open drain or open source from fast output */
 			if (test_bit(GPIOD_FLAG_OPEN_DRAIN, &dflags) ||
 			    test_bit(GPIOD_FLAG_OPEN_SOURCE, &dflags))
-				__clear_bit(descs->ndescs,
-					    array_info->set_mask);
+				__clear_bit(i, array_info->set_mask);
 			/* Identify 'fast' pins which require invertion */
 			if (gpiod_is_active_low(desc))
-				__set_bit(descs->ndescs,
-					  array_info->invert_mask);
+				__set_bit(i, array_info->invert_mask);
 		}
 	}
 	if (array_info)

-- 
2.56.0.506.g506a7eabc5-goog