Re: [PATCH 23/26] media: staging: imgu: use array_size

Julia Lawall
2023-06-27T17:35:56Z

On Fri, 23 Jun 2023, Julia Lawall wrote:

> Use array_size to protect against multiplication overflows.
>
> The changes were done using the following Coccinelle semantic patch:
>
> // <smpl>
> @@
> expression E1, E2;
> constant C1, C2;
> identifier alloc = {vmalloc,vzalloc};
> @@
>
> (
> alloc(C1 * C2,...)
> |
> alloc(
> - (E1) * (E2)
> + array_size(E1, E2)
> ,...)
> )
> // </smpl>
>
> Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
>
> ---
> drivers/staging/media/ipu3/ipu3-mmu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/staging/media/ipu3/ipu3-mmu.c b/drivers/staging/media/ipu3/ipu3-mmu.c
> index cb9bf5fb29a5..9c4adb815c94 100644
> --- a/drivers/staging/media/ipu3/ipu3-mmu.c
> +++ b/drivers/staging/media/ipu3/ipu3-mmu.c
> @@ -464,7 +464,7 @@ struct imgu_mmu_info *imgu_mmu_init(struct device *parent, void __iomem *base)
> * Allocate the array of L2PT CPU pointers, initialized to zero,
> * which means the dummy L2PT allocated above.
> */
> - mmu->l2pts = vzalloc(IPU3_PT_PTES * sizeof(*mmu->l2pts));
> + mmu->l2pts = vzalloc(array_size(IPU3_PT_PTES, sizeof(*mmu->l2pts)));
> if (!mmu->l2pts)
> goto fail_l2pt;

I think that this patch can be dropped. Since it is a multiplcation of
two constants, if there is an overflow, I guess the compiler would detect
it?

julia