gpiolib: Fix NULL pointer deference

Under some circumstances, a gpiochip might be half cleaned from the
gpio_device list.

This patch makes sure that the chip pointer is still valid, before
calling the match function.

[  104.088296] BUG: unable to handle kernel NULL pointer dereference at
0000000000000090
[  104.089772] IP: [<ffffffff813d2045>] of_gpiochip_find_and_xlate+0x15/0x80
[  104.128273] Call Trace:
[  104.129802]  [<ffffffff813d2030>] ? of_parse_own_gpio+0x1f0/0x1f0
[  104.131353]  [<ffffffff813cd910>] gpiochip_find+0x60/0x90
[  104.132868]  [<ffffffff813d21ba>] of_get_named_gpiod_flags+0x9a/0x120
...
[  104.141586]  [<ffffffff8163d12b>] gpio_led_probe+0x11b/0x360

Cc: stable@vger.kernel.org
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 24f60d28f0c0..a2c31a5a677f 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -869,7 +869,7 @@ struct gpio_chip *gpiochip_find(void *data,
 
         spin_lock_irqsave(&gpio_lock, flags);
         list_for_each_entry(gdev, &gpio_devices, list)
-                if (match(gdev->chip, data))
+                if (gdev->chip && match(gdev->chip, data))
                         break;
 
         /* No match? */