On 08/24/2013 11:48 AM, [email protected] wrote:
I got this on an RPi and I can't find anything specific to that. Besides, it's clearly wrong to try to access desc->chip when we have just tested that it may be NULL at drivers/gpio/gpiolib.c:1409:chip = desc->chip; if (chip == NULL) goto done; .... done: if (status) pr_debug("_gpio_request: gpio-%d (%s) status %d\n", desc_to_gpio(desc), label ? : "?", status); To reproduce, just pick an invalid gpio nubmer and: echo -n 248 > /sys/class/gpio/export However, I wasn't able to reproduce it on my laptop, maybe because I don't have any real gpio chips there, not sure. More info on RPi bug report: https://github.com/raspberrypi/linux/issues/364 [ 222.961384] Unable to handle kernel NULL pointer dereference at virtual address 00000044 [ 222.969486] pgd = d97d0000 [ 222.972190] [00000044] *pgd=1aaca831, *pte=00000000, *ppte=00000000 [ 222.978483] Internal error: Oops: 17 [#1] PREEMPT ARM --- drivers/gpio/gpiolib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index d6413b2..e547f75f8b 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -136,7 +136,7 @@ static struct gpio_desc *gpio_to_desc(unsigned gpio) */ static int desc_to_gpio(const struct gpio_desc *desc) { - return desc->chip->base + gpio_chip_hwgpio(desc); + return desc->chip ? desc->chip->base + gpio_chip_hwgpio(desc) : -1; }
Looking into calling code, desc_to_gpio() is clearly not supposed to return an error, and it will result in odd behavior if it returns -1. For example, the resulting debug message of "gpio--1 (...) status ..." is not very useful. It would make more sense to fix the calling code. You could for example validate in affected functions if the gpio pin exists by not only checking for desc but also for desc->chip. Another option might be to have gpio_to_desc() return NULL if desc->chip is NULL. Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
