linux-kernel - Re: [PATCH 20/26] drm/vmwgfx: use array

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Date:   Tue, 27 Jun 2023 19:33:27 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Zack Rusin <zackr@...are.com>
cc:     keescook@...omium.org, kernel-janitors@...r.kernel.org,
        VMware Graphics Reviewers 
        <linux-graphics-maintainer@...are.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 20/26] drm/vmwgfx: 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>
> @@
>     size_t e1,e2;
>     expression COUNT;
>     identifier alloc = {vmalloc,vzalloc,kvmalloc,kvzalloc};
> @@
>
> (
>       alloc(
> -           (e1) * (e2)
> +           array_size(e1, e2)
>       ,...)
> |
>       alloc(
> -           (e1) * (COUNT)
> +           array_size(COUNT, e1)
>       ,...)
> )
> // </smpl>
>
> Signed-off-by: Julia Lawall <Julia.Lawall@...ia.fr>
>
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_devcaps.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_devcaps.c b/drivers/gpu/drm/vmwgfx/vmwgfx_devcaps.c
> index 829df395c2ed..c72fc8111a11 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_devcaps.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_devcaps.c
> @@ -88,7 +88,7 @@ int vmw_devcaps_create(struct vmw_private *vmw)
>  	uint32_t i;
>
>  	if (gb_objects) {
> -		vmw->devcaps = vzalloc(sizeof(uint32_t) * SVGA3D_DEVCAP_MAX);
> +		vmw->devcaps = vzalloc(array_size(SVGA3D_DEVCAP_MAX, sizeof(uint32_t)));
>  		if (!vmw->devcaps)
>  			return -ENOMEM;
>  		for (i = 0; i < SVGA3D_DEVCAP_MAX; ++i) {

Hello,

I think this patch can be dropped, since it's a multiplication of two
constants and no overflow should be possible.

julia