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From: Erick Archer <erick.archer@gmx.com>
To: Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
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	Heiko Stuebner <heiko@sntech.de>,
	=?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= <philmd@linaro.org>,
	Rob Herring <robh@kernel.org>,
	Li Zetao <lizetao1@huawei.com>,
	=?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	Kees Cook <keescook@chromium.org>
Cc: Erick Archer <erick.archer@gmx.com>,
	linux-mtd@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org,
	linux-hardening@vger.kernel.org
Subject: [PATCH v2] mtd: rawnand: Prefer struct_size over open coded arithmetic
Date: Sun, 11 Feb 2024 10:16:33 +0100
Message-Id: <20240211091633.4545-1-erick.archer@gmx.com>
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 cINxvhCxkLxbckyyyVzNI/VQJHstAhTQpdn02cGmDVikI=

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@kernel.org>
Signed-off-by: Erick Archer <erick.archer@gmx.com>
=2D--
Changes in v2:
- Add the "Reviewed-by:" tag.
- Fix a spelling error in the commit message. Change "more safer" for
  "safer" (Uwe Kleine-K=C3=B6nig)
=2D--
 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_na=
nd.c
index 60198e33d2d5..17477bb2d48f 100644
=2D-- 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 =3D devm_kzalloc(dev, sizeof(*chip) + nsels * sizeof(u8),
+	chip =3D devm_kzalloc(dev, struct_size(chip, sels, nsels),
 			    GFP_KERNEL);
 	if (!chip)
 		return -ENOMEM;
=2D-
2.25.1