Re: [PATCH] drm/xe: Prefer struct_size over open coded arithmetic

[Gustavo A. R. Silva]

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@xxxxxxx>

LGTM:

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

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