linux-hardening - Re: [PATCH] drm/xe: Prefer struct

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Date: Sat, 10 Feb 2024 10:49:57 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Erick Archer <erick.archer@....com>,
 Lucas De Marchi <lucas.demarchi@...el.com>, Oded Gabbay
 <ogabbay@...nel.org>, Thomas Hellström
 <thomas.hellstrom@...ux.intel.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 Kees Cook <keescook@...omium.org>
Cc: intel-xe@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] drm/xe: Prefer struct_size over open coded arithmetic

On 2/10/24 08:19, Erick Archer wrote:
> This is an effort to get rid of all multiplications from allocation
> functions in order to prevent integer overflows [1].
> 
> As the "q" variable is a pointer to "struct xe_exec_queue" and this
> structure ends in a flexible array:
> 
> struct xe_exec_queue {
> 	[...]
> 	struct xe_lrc lrc[];
> };
> 
> the preferred way in the kernel is to use the struct_size() helper to
> do the arithmetic instead of the argument "size + size * count" in the
> kzalloc() function.
> 
> This way, the code is more readable and more safer.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
> Link: https://github.com/KSPP/linux/issues/160 [2]
> Signed-off-by: Erick Archer <erick.archer@....com>

LGTM:

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks!
-- 
Gustavo

> ---
>   drivers/gpu/drm/xe/xe_exec_queue.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_exec_queue.c b/drivers/gpu/drm/xe/xe_exec_queue.c
> index bcfc4127c7c5..f4e53cbccd04 100644
> --- a/drivers/gpu/drm/xe/xe_exec_queue.c
> +++ b/drivers/gpu/drm/xe/xe_exec_queue.c
> @@ -44,7 +44,7 @@ static struct xe_exec_queue *__xe_exec_queue_create(struct xe_device *xe,
>   	/* only kernel queues can be permanent */
>   	XE_WARN_ON((flags & EXEC_QUEUE_FLAG_PERMANENT) && !(flags & EXEC_QUEUE_FLAG_KERNEL));
> 
> -	q = kzalloc(sizeof(*q) + sizeof(struct xe_lrc) * width, GFP_KERNEL);
> +	q = kzalloc(struct_size(q, lrc, width), GFP_KERNEL);
>   	if (!q)
>   		return ERR_PTR(-ENOMEM);
> 
> --
> 2.25.1
> 
>