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

[Erick Archer]

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>
---
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