Re: [PATCH] clk: npcm7xx: fix memory allocation

[Kees Cook]

On Thu, Aug 23, 2018 at 4:06 PM, Gustavo A. R. Silva
<gustavo@xxxxxxxxxxxxxx> wrote:
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
>
> struct foo {
>         int stuff;
>         void *entry[];
> };
>
> instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count,
> GFP_KERNEL);
>
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
>
> instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);
>
> Notice that, currently, there is a bug during the allocation:
>
> sizeof(npcm7xx_clk_data) should be sizeof(*npcm7xx_clk_data)
>
> Fix this bug by using struct_size() in kzalloc()
>
> This issue was detected with the help of Coccinelle.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees

> ---
>  drivers/clk/clk-npcm7xx.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/clk-npcm7xx.c b/drivers/clk/clk-npcm7xx.c
> index 740af90..c5edf8f 100644
> --- a/drivers/clk/clk-npcm7xx.c
> +++ b/drivers/clk/clk-npcm7xx.c
> @@ -558,8 +558,8 @@ static void __init npcm7xx_clk_init(struct device_node *clk_np)
>         if (!clk_base)
>                 goto npcm7xx_init_error;
>
> -       npcm7xx_clk_data = kzalloc(sizeof(*npcm7xx_clk_data->hws) *
> -               NPCM7XX_NUM_CLOCKS + sizeof(npcm7xx_clk_data), GFP_KERNEL);
> +       npcm7xx_clk_data = kzalloc(struct_size(npcm7xx_clk_data, hws,
> +                                  NPCM7XX_NUM_CLOCKS), GFP_KERNEL);
>         if (!npcm7xx_clk_data)
>                 goto npcm7xx_init_np_err;
>
> --
> 2.7.4
>



-- 
Kees Cook
Pixel Security