linux-kernel - [PATCH] mtd: rawnand: atmel: use struct_size() in devm

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Date:   Thu, 23 Aug 2018 20:09:38 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Josh Wu <rainyfeeling@...look.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        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>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     linux-mtd@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] mtd: rawnand: atmel: 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 issue was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/mtd/nand/raw/atmel/nand-controller.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/raw/atmel/nand-controller.c b/drivers/mtd/nand/raw/atmel/nand-controller.c
index a068b21..b17cfd0 100644
--- a/drivers/mtd/nand/raw/atmel/nand-controller.c
+++ b/drivers/mtd/nand/raw/atmel/nand-controller.c
@@ -1586,9 +1586,7 @@ static struct atmel_nand *atmel_nand_create(struct atmel_nand_controller *nc,
 		return ERR_PTR(-EINVAL);
 	}
 
-	nand = devm_kzalloc(nc->dev,
-			    sizeof(*nand) + (numcs * sizeof(*nand->cs)),
-			    GFP_KERNEL);
+	nand = devm_kzalloc(nc->dev, struct_size(nand, cs, numcs), GFP_KERNEL);
 	if (!nand) {
 		dev_err(nc->dev, "Failed to allocate NAND object\n");
 		return ERR_PTR(-ENOMEM);
-- 
2.7.4