[PATCH v3] gpio: Remove VLA from stmpe driver

[PATCH v3] gpio: Remove VLA from stmpe driver

[Laura Abbott]

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@redhat.com>
---
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

Re: [PATCH v3] gpio: Remove VLA from stmpe driver

[Phil Reid]

On 29/03/2018 01:59, Laura Abbott 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@redhat.com>
> ---
> 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;
> 
FWIW
Reviewed-by: Phil Reid <preid@electromag.com.au>

-- 
Regards
Phil Reid

Re: [PATCH v3] gpio: Remove VLA from stmpe driver

[Kees Cook]

On Wed, Mar 28, 2018 at 10:59 AM, Laura Abbott <labbott@redhat.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@redhat.com>

Reviewed-by: Kees Cook <keescook@chromium.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

Re: [PATCH v3] gpio: Remove VLA from stmpe driver

[Linus Walleij]

On Wed, Mar 28, 2018 at 7:59 PM, Laura Abbott <labbott@redhat.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@redhat.com>

Patch applied with the review tags!

Yours,
Linus Walleij