linux-kernel - [PATCH] mtd: rawnand: sunxi: Use struct_size() in devm

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Date:   Fri, 4 Jan 2019 11:26:37 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Boris Brezillon <bbrezillon@...nel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>
Cc:     linux-mtd@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] mtd: rawnand: sunxi: Use struct_size() in devm_kzalloc()

One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct foo {
    int stuff;
    void *entry[];
};

instance = devm_kzalloc(dev, sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = devm_kzalloc(dev, struct_size(instance, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/mtd/nand/raw/sunxi_nand.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/mtd/nand/raw/sunxi_nand.c b/drivers/mtd/nand/raw/sunxi_nand.c
index e828ee50a201..f66fffe663bf 100644
--- a/drivers/mtd/nand/raw/sunxi_nand.c
+++ b/drivers/mtd/nand/raw/sunxi_nand.c
@@ -1870,10 +1870,7 @@ static int sunxi_nand_chip_init(struct device *dev, struct sunxi_nfc *nfc,
 		return -EINVAL;
 	}
 
-	chip = devm_kzalloc(dev,
-			    sizeof(*chip) +
-			    (nsels * sizeof(struct sunxi_nand_chip_sel)),
-			    GFP_KERNEL);
+	chip = devm_kzalloc(dev, struct_size(chip, sels, nsels), GFP_KERNEL);
 	if (!chip) {
 		dev_err(dev, "could not allocate chip\n");
 		return -ENOMEM;
-- 
2.20.1