2018-11-15 05:10:43

by Huijin Park

Subject: [PATCH v2] mtd: spi-nor: cast to u64 to avoid uint overflows

From: "huijin.park" <[email protected]>

The "params->size" is defined as "u64".
And "info->sector_size" and "info->n_sectors" are defined as
unsigned int and u16.
Thus, u64 data might have strange data(loss data) if the result
overflows an unsigned int.
This patch casts "info->sector_size" and "info->n_sectors" to an u64.

Signed-off-by: huijin.park <[email protected]>
---
drivers/mtd/spi-nor/spi-nor.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index d9c368c..527f281 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -2459,7 +2459,7 @@ static int spi_nor_init_params(struct spi_nor *nor,
memset(params, 0, sizeof(*params));

/* Set SPI NOR sizes. */
- params->size = info->sector_size * info->n_sectors;
+ params->size = (u64)info->sector_size * (u64)info->n_sectors;
params->page_size = info->page_size;

/* (Fast) Read settings. */
--
1.7.9.5

2018-11-20 08:36:29

by Geert Uytterhoeven

Subject: Re: [PATCH v2] mtd: spi-nor: cast to u64 to avoid uint overflows

Hi Huijin,

On Thu, Nov 15, 2018 at 6:08 AM Huijin Park <[email protected]> wrote:
> From: "huijin.park" <[email protected]>
>
> The "params->size" is defined as "u64".
> And "info->sector_size" and "info->n_sectors" are defined as
> unsigned int and u16.
> Thus, u64 data might have strange data(loss data) if the result
> overflows an unsigned int.
> This patch casts "info->sector_size" and "info->n_sectors" to an u64.
>
> Signed-off-by: huijin.park <[email protected]>
> ---
> drivers/mtd/spi-nor/spi-nor.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index d9c368c..527f281 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -2459,7 +2459,7 @@ static int spi_nor_init_params(struct spi_nor *nor,
> memset(params, 0, sizeof(*params));
>
> /* Set SPI NOR sizes. */
> - params->size = info->sector_size * info->n_sectors;
> + params->size = (u64)info->sector_size * (u64)info->n_sectors;

Adding the cast to only the first operand should be sufficient, and may lead
to faster code, as only a 64x16 multiplication needs to be done, instead of
a 64x64.

> params->page_size = info->page_size;
>
> /* (Fast) Read settings. */

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds