[PATCH 2/6] gpio: fix gpio-chip list corruption

Johan Hovold
2015-01-12T16:12:55Z

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>
---
drivers/gpio/gpiolib.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 89c59f5f1924..ac5944b4e4d8 100644
--- 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;

--
2.0.5