gpio: fix gpio-chip list corruption

Fix potential corruption of gpio-chip list due to failure to remove the
chip from the list before returning in gpiochip_add error path.

The chip could be long gone when the global list is next traversed,
something which could lead to a null-pointer dereference. In the best
case (chip not deallocated) we are just leaking the gpio range.

Fixes: 14e85c0e69d5 ("gpio: remove gpio_descs global array")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 89c59f5..ac5944b 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -248,7 +248,8 @@ int gpiochip_add(struct gpio_chip *chip)
                base = gpiochip_find_base(chip->ngpio);
                if (base < 0) {
                        status = base;
-                       goto unlock;
+                       spin_unlock_irqrestore(&gpio_lock, flags);
+                       goto err_free_descs;
                }
                chip->base = base;
        }
@@ -288,11 +289,8 @@ int gpiochip_add(struct gpio_chip *chip)
        acpi_gpiochip_add(chip);
 
        status = gpiochip_export(chip);
-       if (status) {
-               acpi_gpiochip_remove(chip);
-               of_gpiochip_remove(chip);
-               goto fail;
-       }
+       if (status)
+               goto err_remove_chip;
 
        pr_debug("%s: registered GPIOs %d to %d on device: %s\n", __func__,
                chip->base, chip->base + chip->ngpio - 1,
@@ -300,9 +298,14 @@ int gpiochip_add(struct gpio_chip *chip)
 
        return 0;
 
-unlock:
+err_remove_chip:
+       acpi_gpiochip_remove(chip);
+       of_gpiochip_remove(chip);
+       spin_lock_irqsave(&gpio_lock, flags);
+       list_del(&chip->list);
        spin_unlock_irqrestore(&gpio_lock, flags);
 fail:
+err_free_descs:
        kfree(descs);
        chip->desc = NULL;