[PATCH v2] mtd: rawnand: Prefer struct_size over open coded arithmetic

[Matthias Brugger]

On 11/02/2024 10:16, 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 "chip" variable is a pointer to "struct mtk_nfc_nand_chip" and
> this structure ends in a flexible array:
> 
> struct mtk_nfc_nand_chip {
> 	[...]
> 	u8 sels[] __counted_by(nsels);
> };
> 
> the preferred way in the kernel is to use the struct_size() helper to
> do the arithmetic instead of the argument "size + count * size" in the
> devm_kzalloc() function.
> 
> This way, the code is more readable and 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]
> Reviewed-by: Gustavo A. R. Silva <gustavoars at kernel.org>
> Signed-off-by: Erick Archer <erick.archer at gmx.com>

Reviewed-by: Matthias Brugger <matthias.bgg at gmail.com>

> ---
> Changes in v2:
> - Add the "Reviewed-by:" tag.
> - Fix a spelling error in the commit message. Change "more safer" for
>    "safer" (Uwe Kleine-König)
> ---
>   drivers/mtd/nand/raw/mtk_nand.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/raw/mtk_nand.c b/drivers/mtd/nand/raw/mtk_nand.c
> index 60198e33d2d5..17477bb2d48f 100644
> --- a/drivers/mtd/nand/raw/mtk_nand.c
> +++ b/drivers/mtd/nand/raw/mtk_nand.c
> @@ -1356,7 +1356,7 @@ static int mtk_nfc_nand_chip_init(struct device *dev, struct mtk_nfc *nfc,
>   		return -EINVAL;
>   	}
> 
> -	chip = devm_kzalloc(dev, sizeof(*chip) + nsels * sizeof(u8),
> +	chip = devm_kzalloc(dev, struct_size(chip, sels, nsels),
>   			    GFP_KERNEL);
>   	if (!chip)
>   		return -ENOMEM;
> --
> 2.25.1
>