linux-kernel - Re: [PATCH v2 03/24] drm/gud: use vmalloc

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Date:   Mon, 3 Jul 2023 14:23:45 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Julia Lawall <Julia.Lawall@...ia.fr>,
        Noralf Trønnes <noralf@...nnes.org>
Cc:     keescook@...omium.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        christophe.jaillet@...adoo.fr, kuba@...nel.org
Subject: Re: [PATCH v2 03/24] drm/gud: use vmalloc_array and vcalloc



Am 27.06.23 um 16:43 schrieb Julia Lawall:
> Use vmalloc_array and vcalloc to protect against
> multiplication overflows.
> 
> The changes were done using the following Coccinelle
> semantic patch:
> 
> // <smpl>
> @initialize:ocaml@
> @@
> 
> let rename alloc =
>    match alloc with
>      "vmalloc" -> "vmalloc_array"
>    | "vzalloc" -> "vcalloc"
>    | _ -> failwith "unknown"
> 
> @@
>      size_t e1,e2;
>      constant C1, C2;
>      expression E1, E2, COUNT, x1, x2, x3;
>      typedef u8;
>      typedef __u8;
>      type t = {u8,__u8,char,unsigned char};
>      identifier alloc = {vmalloc,vzalloc};
>      fresh identifier realloc = script:ocaml(alloc) { rename alloc };
> @@
> 
> (
>        alloc(x1*x2*x3)
> |
>        alloc(C1 * C2)
> |
>        alloc((sizeof(t)) * (COUNT), ...)
> |
> -     alloc((e1) * (e2))
> +     realloc(e1, e2)
> |
> -     alloc((e1) * (COUNT))
> +     realloc(COUNT, e1)
> |
> -     alloc((E1) * (E2))
> +     realloc(E1, E2)
> )
> // </smpl>
> 
> Signed-off-by: Julia Lawall <Julia.Lawall@...ia.fr>

Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>

> 
> ---
> v2: Use vmalloc_array and vcalloc instead of array_size.
> This also leaves a multiplication of a constant by a sizeof
> as is.  Two patches are thus dropped from the series.
> 
>   drivers/gpu/drm/gud/gud_pipe.c |    2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff -u -p a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
> --- a/drivers/gpu/drm/gud/gud_pipe.c
> +++ b/drivers/gpu/drm/gud/gud_pipe.c
> @@ -390,7 +390,7 @@ static int gud_fb_queue_damage(struct gu
>   	mutex_lock(&gdrm->damage_lock);
>   
>   	if (!gdrm->shadow_buf) {
> -		gdrm->shadow_buf = vzalloc(fb->pitches[0] * fb->height);
> +		gdrm->shadow_buf = vcalloc(fb->pitches[0], fb->height);
>   		if (!gdrm->shadow_buf) {
>   			mutex_unlock(&gdrm->damage_lock);
>   			return -ENOMEM;
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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