linux-hardening - Re: [PATCH v2] mtd: rawnand: Prefer struct

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Message-ID: <f5ea54f4-9176-4fde-89bf-71b1771e47c3@gmail.com>
Date: Mon, 12 Feb 2024 16:50:51 +0100
From: Matthias Brugger <matthias.bgg@...il.com>
To: Erick Archer <erick.archer@....com>,
 Miquel Raynal <miquel.raynal@...tlin.com>,
 Richard Weinberger <richard@....at>, Vignesh Raghavendra <vigneshr@...com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
 Heiko Stuebner <heiko@...ech.de>, Philippe Mathieu-Daudé
 <philmd@...aro.org>, Rob Herring <robh@...nel.org>,
 Li Zetao <lizetao1@...wei.com>,
 Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 Kees Cook <keescook@...omium.org>
Cc: linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] mtd: rawnand: Prefer struct_size over open coded
 arithmetic

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@...nel.org>
> Signed-off-by: Erick Archer <erick.archer@....com>

Reviewed-by: Matthias Brugger <matthias.bgg@...il.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
>