Re: [PATCH] [BUGFIX] gpio: reject invalid gpio before getting gpio_desc
From: Masami Hiramatsu
Date: Sun Jul 30 2017 - 20:54:18 EST
On Sun, 30 Jul 2017 19:21:36 +0300
Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote:
> On Sat, Jul 29, 2017 at 11:00 AM, Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
> > Check user-given gpio number and reject it before
> > calling gpio_to_desc() because gpio_to_desc() is
> > for kernel driver and it expects given gpio number
> > is valid (means 0 to 511).
>
> > If given number is invalid, gpio_to_desc() calls
> > WARN() and dump registers and stack for debug.
> > This means user can easily kick WARN() just by
> > writing invalid gpio number (e.g. 512) to
> > /sys/class/gpio/export.
>
> > This bug has been introduced by commit 0e9a5edf5d01
> > ("gpio: fix deferred probe detection for legacy API")
>
> Why so narrow paraghraps? We don't do two column articles :-)
OK, I'll remove this, since Fixes explain that.
>
> > Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > Fixes: commit 0e9a5edf5d01 ("gpio: fix deferred probe detection for legacy API")
>
> If you use git tools directly, like
>
> % git commit -s --amend
>
> you will immediately notice that your SoB line is supposed to be the last one.
I'll move SoB line to the bottom.
>
> Besides above, word "commit" is not needed in Fixes: tag IIRC.
Ah, OK, I'll remove "commit" from Fixes.
>
>
> > --- a/drivers/gpio/gpiolib-sysfs.c
> > +++ b/drivers/gpio/gpiolib-sysfs.c
> > @@ -2,6 +2,7 @@
> > #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>
>
> > @@ -443,14 +444,16 @@ static ssize_t export_store(struct class *class,
>
> > - struct gpio_desc *desc;
> > + struct gpio_desc *desc = NULL;
>
> > - desc = gpio_to_desc(gpio);
> > + if (gpio_is_valid(gpio))
> > + desc = gpio_to_desc(gpio);
>
> Twice repeatition is a candidate for a helper, like:
>
> static inline struct gpio_desc *gpio_to_valid_desc(int gpio)
> {
> return gpio_is_valid(gpio) ? gpio_to_desc(gpio) : NULL;
> }
OK, I'll add the helper.
Thanks,
--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>