[PATCH v2 4/5] gpiolib: don't overwrite the entire flags field in gpiod_free_commit()

[Bartosz Golaszewski]

Use gpiod_update_flags() to clear all request-related flags in one go
instead of risking racing with concurrent users and overwriting any
changes they could have done between READ_ONCE() and WRITE_ONCE().

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 35b545332b80 ("gpio: remove gpio_lock")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
---
 drivers/gpio/gpiolib.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index af2d67d977f4925558ab77c34b37c3c29bd12a6f..4c9c524389ca13e422bca8c217b7f47477cc0dd4 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -3,6 +3,7 @@
 #include <linux/acpi.h>
 #include <linux/array_size.h>
 #include <linux/bitmap.h>
+#include <linux/bitops.h>
 #include <linux/cleanup.h>
 #include <linux/compat.h>
 #include <linux/debugfs.h>
@@ -2696,24 +2697,23 @@ void gpiod_free_commit(struct gpio_desc *desc)
 #ifdef CONFIG_GPIO_CDEV
 		WRITE_ONCE(desc->debounce_period_us, 0);
 #endif
-
-		clear_bit(GPIOD_FLAG_ACTIVE_LOW, &flags);
-		clear_bit(GPIOD_FLAG_REQUESTED, &flags);
-		clear_bit(GPIOD_FLAG_OPEN_DRAIN, &flags);
-		clear_bit(GPIOD_FLAG_OPEN_SOURCE, &flags);
-		clear_bit(GPIOD_FLAG_PULL_UP, &flags);
-		clear_bit(GPIOD_FLAG_PULL_DOWN, &flags);
-		clear_bit(GPIOD_FLAG_BIAS_DISABLE, &flags);
-		clear_bit(GPIOD_FLAG_EDGE_RISING, &flags);
-		clear_bit(GPIOD_FLAG_EDGE_FALLING, &flags);
-		clear_bit(GPIOD_FLAG_EVENT_CLOCK_REALTIME, &flags);
-		clear_bit(GPIOD_FLAG_EVENT_CLOCK_HTE, &flags);
-		clear_bit(GPIOD_FLAG_IS_HOGGED, &flags);
 #ifdef CONFIG_OF_DYNAMIC
 		WRITE_ONCE(desc->hog, NULL);
 #endif
 		desc_set_label(desc, NULL);
-		WRITE_ONCE(desc->flags, flags);
+		set_mask_bits(&desc->flags,
+				   BIT(GPIOD_FLAG_ACTIVE_LOW) |
+				   BIT(GPIOD_FLAG_REQUESTED) |
+				   BIT(GPIOD_FLAG_OPEN_DRAIN) |
+				   BIT(GPIOD_FLAG_OPEN_SOURCE) |
+				   BIT(GPIOD_FLAG_PULL_UP) |
+				   BIT(GPIOD_FLAG_PULL_DOWN) |
+				   BIT(GPIOD_FLAG_BIAS_DISABLE) |
+				   BIT(GPIOD_FLAG_EDGE_RISING) |
+				   BIT(GPIOD_FLAG_EDGE_FALLING) |
+				   BIT(GPIOD_FLAG_EVENT_CLOCK_REALTIME) |
+				   BIT(GPIOD_FLAG_EVENT_CLOCK_HTE) |
+				   BIT(GPIOD_FLAG_IS_HOGGED), 0);
 		gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_RELEASED);
 	}
 }

-- 
2.47.3