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Date: Fri, 30 Mar 2018 17:33:55 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Laura Abbott <labbott@...hat.com>
Cc: Linus Walleij <linus.walleij@...aro.org>, Kees Cook <keescook@...omium.org>,
Lukas Wunner <lukas@...ner.de>, "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, kernel-hardening@...ts.openwall.com,
Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [PATCHv3] gpio: Remove VLA from gpiolib
On Wed, Mar 28, 2018 at 9:18 PM, Laura Abbott <labbott@...hat.com> wrote:
> The new challenge is to remove VLAs from the kernel
> (see https://lkml.org/lkml/2018/3/7/621) to eventually
> turn on -Wvla.
>
> Using a kmalloc array is the easy way to fix this but kmalloc is still
> more expensive than stack allocation. Introduce a fast path with a
> fixed size stack array to cover most chip with gpios below some fixed
> amount. The slow path dynamically allocates an array to cover those
> chips with a large number of gpios.
> + ret = gpiod_set_array_value_complex(false,
> true,
> lh->numdescs,
> lh->descs,
> vals);
> + if (ret)
> + return ret;
> +
> return 0;
Can't we
return gpiod_set_array_value_complex(); ?
> + slowpath = kcalloc(2 * BITS_TO_LONGS(chip->ngpio),
> + sizeof(*slowpath),
> + can_sleep ? GFP_KERNEL : GFP_ATOMIC);
> + if (slowpath)
> + kfree(slowpath);
> + if (slowpath)
> + kfree(slowpath);
Since slowpath is a pointer, conditionals above are redundant.
> + slowpath = kcalloc(2 * BITS_TO_LONGS(chip->ngpio),
> + sizeof(*slowpath),
> + can_sleep ? GFP_KERNEL : GFP_ATOMIC);
> + if (slowpath)
> + kfree(slowpath);
Ditto.
--
With Best Regards,
Andy Shevchenko
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