[PATCH 6/8] gpiolib: sanitize the return value of gpio_chip::direction_output()

From: Bartosz Golaszewski
Date: Mon Feb 10 2025 - 05:56:37 EST


From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>

The return value of the direction_output() callback may be propagated to
user-space. As per the API contract it can only return 0 or a negative
error number. Add a wrapper around the callback calls that filters out
anything else.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
---
drivers/gpio/gpiolib.c | 25 +++++++++++++++++++++----
1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 7255f4df6a8b..1f75ae6e208c 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2683,6 +2683,23 @@ int gpio_set_debounce_timeout(struct gpio_desc *desc, unsigned int debounce)
return ret;
}

+static int gpiochip_direction_output(struct gpio_chip *gc, unsigned int offset,
+ int value)
+{
+ int ret;
+
+ lockdep_assert_held(&gc->gpiodev->srcu);
+
+ if (WARN_ON(!gc->direction_output))
+ return -EOPNOTSUPP;
+
+ ret = gc->direction_output(gc, offset, value);
+ if (ret > 0)
+ ret = -EBADE;
+
+ return ret;
+}
+
/**
* gpiod_direction_input - set the GPIO direction to input
* @desc: GPIO to set to input
@@ -2780,8 +2797,8 @@ static int gpiod_direction_output_raw_commit(struct gpio_desc *desc, int value)
}

if (guard.gc->direction_output) {
- ret = guard.gc->direction_output(guard.gc,
- gpio_chip_hwgpio(desc), val);
+ ret = gpiochip_direction_output(guard.gc,
+ gpio_chip_hwgpio(desc), val);
} else {
/* Check that we are in output mode if we can */
if (guard.gc->get_direction) {
@@ -3433,7 +3450,7 @@ static void gpio_set_open_drain_value_commit(struct gpio_desc *desc, bool value)
if (value) {
ret = guard.gc->direction_input(guard.gc, offset);
} else {
- ret = guard.gc->direction_output(guard.gc, offset, 0);
+ ret = gpiochip_direction_output(guard.gc, offset, 0);
if (!ret)
set_bit(FLAG_IS_OUT, &desc->flags);
}
@@ -3458,7 +3475,7 @@ static void gpio_set_open_source_value_commit(struct gpio_desc *desc, bool value
return;

if (value) {
- ret = guard.gc->direction_output(guard.gc, offset, 1);
+ ret = gpiochip_direction_output(guard.gc, offset, 1);
if (!ret)
set_bit(FLAG_IS_OUT, &desc->flags);
} else {

--
2.45.2