gpiolib: check descriptors validity before use

Some functions dereferenced their GPIO descriptor argument without
checking its validity first, potentially leading to an oops when given
an invalid argument.

This patch also makes gpio_get_value() more resilient when given an
invalid GPIO, returning 0 instead of silently crashing.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Cc: Ryan Mallon <rmallon@gmail.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/gpio/gpiolib.c

@@ -174,7 +174,7 @@ static int gpio_ensure_requested(struct gpio_desc *desc)
 /* caller holds gpio_lock *OR* gpio is marked as requested */
 static struct gpio_chip *gpiod_to_chip(struct gpio_desc *desc)
 {
-	return desc->chip;
+	return desc ? desc->chip : NULL;
 }
 
 struct gpio_chip *gpio_to_chip(unsigned gpio)
@@ -654,6 +654,11 @@ static ssize_t export_store(struct class *class,
 		goto done;
 
 	desc = gpio_to_desc(gpio);
+	/* reject invalid GPIOs */
+	if (!desc) {
+		pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
+		return -EINVAL;
+	}
 
 	/* No extra locking here; FLAG_SYSFS just signifies that the
 	 * request and export were done by on behalf of userspace, so
@@ -690,12 +695,14 @@ static ssize_t unexport_store(struct class *class,
 	if (status < 0)
 		goto done;
 
-	status = -EINVAL;
-
 	desc = gpio_to_desc(gpio);
 	/* reject bogus commands (gpio_unexport ignores them) */
-	if (!desc)
-		goto done;
+	if (!desc) {
+		pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
+		return -EINVAL;
+	}
+
+	status = -EINVAL;
 
 	/* No extra locking here; FLAG_SYSFS just signifies that the
 	 * request and export were done by on behalf of userspace, so
@@ -846,8 +853,10 @@ static int gpiod_export_link(struct device *dev, const char *name,
 {
 	int			status = -EINVAL;
 
-	if (!desc)
-		goto done;
+	if (!desc) {
+		pr_warn("%s: invalid GPIO\n", __func__);
+		return -EINVAL;
+	}
 
 	mutex_lock(&sysfs_lock);
 
@@ -865,7 +874,6 @@ static int gpiod_export_link(struct device *dev, const char *name,
 
 	mutex_unlock(&sysfs_lock);
 
-done:
 	if (status)
 		pr_debug("%s: gpio%d status %d\n", __func__, desc_to_gpio(desc),
 			 status);
@@ -896,8 +904,10 @@ static int gpiod_sysfs_set_active_low(struct gpio_desc *desc, int value)
 	struct device		*dev = NULL;
 	int			status = -EINVAL;
 
-	if (!desc)
-		goto done;
+	if (!desc) {
+		pr_warn("%s: invalid GPIO\n", __func__);
+		return -EINVAL;
+	}
 
 	mutex_lock(&sysfs_lock);
 
@@ -914,7 +924,6 @@ static int gpiod_sysfs_set_active_low(struct gpio_desc *desc, int value)
 unlock:
 	mutex_unlock(&sysfs_lock);
 
-done:
 	if (status)
 		pr_debug("%s: gpio%d status %d\n", __func__, desc_to_gpio(desc),
 			 status);
@@ -940,8 +949,8 @@ static void gpiod_unexport(struct gpio_desc *desc)
 	struct device		*dev = NULL;
 
 	if (!desc) {
-		status = -EINVAL;
-		goto done;
+		pr_warn("%s: invalid GPIO\n", __func__);
+		return;
 	}
 
 	mutex_lock(&sysfs_lock);
@@ -962,7 +971,7 @@ static void gpiod_unexport(struct gpio_desc *desc)
 		device_unregister(dev);
 		put_device(dev);
 	}
-done:
+
 	if (status)
 		pr_debug("%s: gpio%d status %d\n", __func__, desc_to_gpio(desc),
 			 status);
@@ -1384,12 +1393,13 @@ static int gpiod_request(struct gpio_desc *desc, const char *label)
 	int			status = -EPROBE_DEFER;
 	unsigned long		flags;
 
-	spin_lock_irqsave(&gpio_lock, flags);
-
 	if (!desc) {
-		status = -EINVAL;
-		goto done;
+		pr_warn("%s: invalid GPIO\n", __func__);
+		return -EINVAL;
 	}
+
+	spin_lock_irqsave(&gpio_lock, flags);
+
 	chip = desc->chip;
 	if (chip == NULL)
 		goto done;
@@ -1432,8 +1442,7 @@ static int gpiod_request(struct gpio_desc *desc, const char *label)
 done:
 	if (status)
 		pr_debug("_gpio_request: gpio-%d (%s) status %d\n",
-			 desc ? desc_to_gpio(desc) : -1,
-			 label ? : "?", status);
+			 desc_to_gpio(desc), label ? : "?", status);
 	spin_unlock_irqrestore(&gpio_lock, flags);
 	return status;
 }
@@ -1616,10 +1625,13 @@ static int gpiod_direction_input(struct gpio_desc *desc)
 	int			status = -EINVAL;
 	int			offset;
 
+	if (!desc) {
+		pr_warn("%s: invalid GPIO\n", __func__);
+		return -EINVAL;
+	}
+
 	spin_lock_irqsave(&gpio_lock, flags);
 
-	if (!desc)
-		goto fail;
 	chip = desc->chip;
 	if (!chip || !chip->get || !chip->direction_input)
 		goto fail;
@@ -1655,13 +1667,9 @@ lose:
 	return status;
 fail:
 	spin_unlock_irqrestore(&gpio_lock, flags);
-	if (status) {
-		int gpio = -1;
-		if (desc)
-			gpio = desc_to_gpio(desc);
-		pr_debug("%s: gpio-%d status %d\n",
-			__func__, gpio, status);
-	}
+	if (status)
+		pr_debug("%s: gpio-%d status %d\n", __func__,
+			 desc_to_gpio(desc), status);
 	return status;
 }
 
@@ -1678,6 +1686,11 @@ static int gpiod_direction_output(struct gpio_desc *desc, int value)
 	int			status = -EINVAL;
 	int offset;
 
+	if (!desc) {
+		pr_warn("%s: invalid GPIO\n", __func__);
+		return -EINVAL;
+	}
+
 	/* Open drain pin should not be driven to 1 */
 	if (value && test_bit(FLAG_OPEN_DRAIN,  &desc->flags))
 		return gpiod_direction_input(desc);
@@ -1688,8 +1701,6 @@ static int gpiod_direction_output(struct gpio_desc *desc, int value)
 
 	spin_lock_irqsave(&gpio_lock, flags);
 
-	if (!desc)
-		goto fail;
 	chip = desc->chip;
 	if (!chip || !chip->set || !chip->direction_output)
 		goto fail;
@@ -1725,13 +1736,9 @@ lose:
 	return status;
 fail:
 	spin_unlock_irqrestore(&gpio_lock, flags);
-	if (status) {
-		int gpio = -1;
-		if (desc)
-			gpio = desc_to_gpio(desc);
-		pr_debug("%s: gpio-%d status %d\n",
-			__func__, gpio, status);
-	}
+	if (status)
+		pr_debug("%s: gpio-%d status %d\n", __func__,
+			 desc_to_gpio(desc), status);
 	return status;
 }
 
@@ -1753,10 +1760,13 @@ static int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
 	int			status = -EINVAL;
 	int			offset;
 
+	if (!desc) {
+		pr_warn("%s: invalid GPIO\n", __func__);
+		return -EINVAL;
+	}
+
 	spin_lock_irqsave(&gpio_lock, flags);
 
-	if (!desc)
-		goto fail;
 	chip = desc->chip;
 	if (!chip || !chip->set || !chip->set_debounce)
 		goto fail;
@@ -1776,13 +1786,9 @@ static int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
 
 fail:
 	spin_unlock_irqrestore(&gpio_lock, flags);
-	if (status) {
-		int gpio = -1;
-		if (desc)
-			gpio = desc_to_gpio(desc);
-		pr_debug("%s: gpio-%d status %d\n",
-			__func__, gpio, status);
-	}
+	if (status)
+		pr_debug("%s: gpio-%d status %d\n", __func__,
+			 desc_to_gpio(desc), status);
 
 	return status;
 }
@@ -1830,6 +1836,8 @@ static int gpiod_get_value(struct gpio_desc *desc)
 	int value;
 	int offset;
 
+	if (!desc)
+		return 0;
 	chip = desc->chip;
 	offset = gpio_chip_hwgpio(desc);
 	/* Should be using gpio_get_value_cansleep() */
@@ -1912,6 +1920,8 @@ static void gpiod_set_value(struct gpio_desc *desc, int value)
 {
 	struct gpio_chip	*chip;
 
+	if (!desc)
+		return;
 	chip = desc->chip;
 	/* Should be using gpio_set_value_cansleep() */
 	WARN_ON(chip->can_sleep);
@@ -1940,6 +1950,8 @@ EXPORT_SYMBOL_GPL(__gpio_set_value);
  */
 static int gpiod_cansleep(struct gpio_desc *desc)
 {
+	if (!desc)
+		return 0;
 	/* only call this on GPIOs that are valid! */
 	return desc->chip->can_sleep;
 }
@@ -1964,6 +1976,8 @@ static int gpiod_to_irq(struct gpio_desc *desc)
 	struct gpio_chip	*chip;
 	int			offset;
 
+	if (!desc)
+		return -EINVAL;
 	chip = desc->chip;
 	offset = gpio_chip_hwgpio(desc);
 	return chip->to_irq ? chip->to_irq(chip, offset) : -ENXIO;
@@ -1987,6 +2001,8 @@ static int gpiod_get_value_cansleep(struct gpio_desc *desc)
 	int offset;
 
 	might_sleep_if(extra_checks);
+	if (!desc)
+		return 0;
 	chip = desc->chip;
 	offset = gpio_chip_hwgpio(desc);
 	value = chip->get ? chip->get(chip, offset) : 0;
@@ -2005,6 +2021,8 @@ static void gpiod_set_value_cansleep(struct gpio_desc *desc, int value)
 	struct gpio_chip	*chip;
 
 	might_sleep_if(extra_checks);
+	if (!desc)
+		return;
 	chip = desc->chip;
 	trace_gpio_value(desc_to_gpio(desc), 0, value);
 	if (test_bit(FLAG_OPEN_DRAIN,  &desc->flags))