linux-kernel - Re: [PATCH v1 2/2] gpiolib: of: Integrate of_gpiochip_init_valid_mask() into gpiochip_init_valid

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Date:   Mon, 7 Nov 2022 13:40:53 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v1 2/2] gpiolib: of: Integrate
 of_gpiochip_init_valid_mask() into gpiochip_init_valid_mask()

On Mon, Nov 07, 2022 at 11:09:19PM +0200, Andy Shevchenko wrote:
> On Mon, Nov 07, 2022 at 10:20:37AM -0800, Dmitry Torokhov wrote:
> > On Mon, Nov 07, 2022 at 06:10:27PM +0200, Andy Shevchenko wrote:
> > > +static unsigned int gpiochip_count_reserved_ranges(struct gpio_chip *gc)
> > > +{
> > > +	int size;
> > > +
> > > +	size = fwnode_property_count_u32(gc->fwnode, "gpio-reserved-ranges");
> > 
> > I wonder if a comment why we need even size would not be helpful.
> 
> Was it in the original code?
> Anyway, if Bart thinks so as well, I may add it in v2.
> 
> > > +	if (size > 0 && size % 2 == 0)
> > > +		return size;
> > > +
> > > +	return 0;
> > > +}
> > > +
> > >  static int gpiochip_alloc_valid_mask(struct gpio_chip *gc)
> > >  {
> > > -	if (!(of_gpio_need_valid_mask(gc) || gc->init_valid_mask))
> > > +	if (!(gpiochip_count_reserved_ranges(gc) || gc->init_valid_mask))
> > >  		return 0;
> > >  
> > >  	gc->valid_mask = gpiochip_allocate_mask(gc);
> > > @@ -457,8 +468,47 @@ static int gpiochip_alloc_valid_mask(struct gpio_chip *gc)
> > >  	return 0;
> > >  }
> > >  
> > > +static int gpiochip_apply_reserved_ranges(struct gpio_chip *gc, unsigned int sz)
> > > +{
> > > +	u32 *ranges;
> > > +	int ret;
> > > +
> > > +	ranges = kmalloc_array(sz, sizeof(*ranges), GFP_KERNEL);
> > > +	if (!ranges)
> > > +		return -ENOMEM;
> > > +
> > > +	ret = fwnode_property_read_u32_array(gc->fwnode, "gpio-reserved-ranges", ranges, sz);
> > > +	if (ret) {
> > > +		kfree(ranges);
> > > +		return ret;
> > > +	}
> > > +
> > > +	while (sz) {
> > > +		u32 count = ranges[--sz];
> > > +		u32 start = ranges[--sz];
> > 
> > I know we checked sz validity, but I wonder if re-checking it in this
> > function would not insulate us from errors creeping in after some other
> > code refactoring.
> 
> I'm not sure I understand what you meant. The fwnode_property_read_u32_array()
> will fail if the given sz is too big for the real data, so while (sz) would
> never even go on the invalid data.

I am more worried about sz being odd and the loop ending up trying to
dereference ranges[-1].

Thanks.

-- 
Dmitry