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Message-ID: <CAGXu5jJwPbUHherfpPbyN8o9NntKN_CYY_TRyvrd+K_LSvZMFw@mail.gmail.com>
Date: Wed, 23 May 2018 15:51:48 -0700
From: Kees Cook <keescook@...omium.org>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Laura Abbott <labbott@...hat.com>, Patrice Chotard <patrice.chotard@...com>,
linux-gpio@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v3] gpio: Remove VLA from stmpe driver
On Wed, Mar 28, 2018 at 10:59 AM, 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)
>
> The number of GPIOs on the supported chips is fairly small
> so stack allocate to a known upper bound and spit out a warning
> if any new chips have more gpios.
>
> Signed-off-by: Laura Abbott <labbott@...hat.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Linus, I think this patch is still needed and got missed? Can you take
it as well?
Thanks!
-Kees
> ---
> v3: Split this off from the rest of the series since some of the
> patches had been picked up. Switched to just hardcoding an upper
> bound for the stack array since it's only a few extra bytes
> of stack space.
> ---
> drivers/gpio/gpio-stmpe.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpio-stmpe.c b/drivers/gpio/gpio-stmpe.c
> index f8d7d1cd8488..8d6a5a7e612d 100644
> --- a/drivers/gpio/gpio-stmpe.c
> +++ b/drivers/gpio/gpio-stmpe.c
> @@ -363,13 +363,15 @@ static struct irq_chip stmpe_gpio_irq_chip = {
> .irq_set_type = stmpe_gpio_irq_set_type,
> };
>
> +#define MAX_GPIOS 24
> +
> static irqreturn_t stmpe_gpio_irq(int irq, void *dev)
> {
> struct stmpe_gpio *stmpe_gpio = dev;
> struct stmpe *stmpe = stmpe_gpio->stmpe;
> u8 statmsbreg;
> int num_banks = DIV_ROUND_UP(stmpe->num_gpios, 8);
> - u8 status[num_banks];
> + u8 status[DIV_ROUND_UP(MAX_GPIOS, 8)];
> int ret;
> int i;
>
> @@ -434,6 +436,11 @@ static int stmpe_gpio_probe(struct platform_device *pdev)
> struct stmpe_gpio *stmpe_gpio;
> int ret, irq;
>
> + if (stmpe->num_gpios > MAX_GPIOS) {
> + dev_err(&pdev->dev, "Need to increase maximum GPIO number\n");
> + return -EINVAL;
> + }
> +
> stmpe_gpio = kzalloc(sizeof(*stmpe_gpio), GFP_KERNEL);
> if (!stmpe_gpio)
> return -ENOMEM;
> --
> 2.14.3
>
--
Kees Cook
Pixel Security
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