linux-kernel - Re: [PATCH] drm/tiny: Use kmalloc

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Message-ID: <712a27fc6c4060e67b3da58cb8564387b40b5971@intel.com>
Date: Tue, 23 Sep 2025 16:51:40 +0300
From: Jani Nikula <jani.nikula@...ux.intel.com>
To: Rahul Kumar <rk0006818@...il.com>, lanzano.alex@...il.com,
 maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
 tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-kernel-mentees@...ts.linuxfoundation.org, skhan@...uxfoundation.org,
 rk0006818@...il.com
Subject: Re: [PATCH] drm/tiny: Use kmalloc_array() instead of kmalloc()

On Tue, 23 Sep 2025, Rahul Kumar <rk0006818@...il.com> wrote:
> Documentation/process/deprecated.rst recommends against the use of
> kmalloc with dynamic size calculations due to the risk of overflow and
> smaller allocation being made than the caller was expecting.
>
> Replace kmalloc() with kmalloc_array() in drivers/gpu/drm/tiny/repaper.c
> to make the intended allocation size clearer and avoid potential overflow
> issues.
>
> Signed-off-by: Rahul Kumar <rk0006818@...il.com>
> ---
>  drivers/gpu/drm/tiny/repaper.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/tiny/repaper.c b/drivers/gpu/drm/tiny/repaper.c
> index 5c3b51eb0a97..4d439a2d973a 100644
> --- a/drivers/gpu/drm/tiny/repaper.c
> +++ b/drivers/gpu/drm/tiny/repaper.c
> @@ -535,7 +535,7 @@ static int repaper_fb_dirty(struct drm_framebuffer *fb,
>  	DRM_DEBUG("Flushing [FB:%d] st=%ums\n", fb->base.id,
>  		  epd->factored_stage_time);
>  
> -	buf = kmalloc(fb->width * fb->height / 8, GFP_KERNEL);
> +	buf = kmalloc_array(fb->width, fb->height / 8, GFP_KERNEL);

That's just not the same thing, though.

BR,
Jani.

>  	if (!buf) {
>  		ret = -ENOMEM;
>  		goto out_exit;

-- 
Jani Nikula, Intel