linux-kernel - Re: [PATCH 23/26] media: staging: imgu: use array

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Date:   Tue, 27 Jun 2023 19:35:47 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Julia Lawall <Julia.Lawall@...ia.fr>
cc:     Sakari Ailus <sakari.ailus@...ux.intel.com>, keescook@...omium.org,
        kernel-janitors@...r.kernel.org, Bingbu Cao <bingbu.cao@...el.com>,
        Tianshu Qiu <tian.shu.qiu@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-media@...r.kernel.org, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 23/26] media: staging: imgu: use array_size



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@...ia.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