[PATCH] gpio: Do not trigger WARN() with sysfs gpio export/unexport

[Damien Le Moal <damien.lemoal@xxxxxxx>]

If a user tries to export or unexport an invalid gpio (e.g. gpio number
>= ARCH_NR_GPIOS), gpio_to_desc() will trigger a register dump through a
WARN() call. Avoid this rather scary error message by first checking the
validity of the gpio number before calling gpio_to_desc() in
export_store() and unexport_store(). The user gets a normal error
message to signal his/her error without any possible confusion with a
kernel bug.

Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
---
 drivers/gpio/gpiolib-sysfs.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 728f6c687182..b6fd0d82757a 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -3,6 +3,7 @@
 #include <linux/mutex.h>
 #include <linux/device.h>
 #include <linux/sysfs.h>
+#include <linux/gpio.h>
 #include <linux/gpio/consumer.h>
 #include <linux/gpio/driver.h>
 #include <linux/interrupt.h>
@@ -456,14 +457,15 @@ static ssize_t export_store(struct class *class,
 				const char *buf, size_t len)
 {
 	long			gpio;
-	struct gpio_desc	*desc;
+	struct gpio_desc	*desc = NULL;
 	int			status;
 
 	status = kstrtol(buf, 0, &gpio);
 	if (status < 0)
 		goto done;
 
-	desc = gpio_to_desc(gpio);
+	if (gpio_is_valid(gpio))
+		desc = gpio_to_desc(gpio);
 	/* reject invalid GPIOs */
 	if (!desc) {
 		pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
@@ -503,14 +505,15 @@ static ssize_t unexport_store(struct class *class,
 				const char *buf, size_t len)
 {
 	long			gpio;
-	struct gpio_desc	*desc;
+	struct gpio_desc	*desc = NULL;
 	int			status;
 
 	status = kstrtol(buf, 0, &gpio);
 	if (status < 0)
 		goto done;
 
-	desc = gpio_to_desc(gpio);
+	if (gpio_is_valid(gpio))
+		desc = gpio_to_desc(gpio);
 	/* reject bogus commands (gpio_unexport ignores them) */
 	if (!desc) {
 		pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
-- 
2.28.0