linux-kernel - [PATCH] serial: max310x: Use struct_size() in devm

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Message-ID: <20190104213913.GA21248@embeddedor>
Date:   Fri, 4 Jan 2019 15:39:13 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] serial: max310x: 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/tty/serial/max310x.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index 4f479841769a..1d700a8ab517 100644
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -1197,8 +1197,7 @@ static int max310x_probe(struct device *dev, struct max310x_devtype *devtype,
 		return PTR_ERR(regmap);
 
 	/* Alloc port structure */
-	s = devm_kzalloc(dev, sizeof(*s) +
-			 sizeof(struct max310x_one) * devtype->nr, GFP_KERNEL);
+	s = devm_kzalloc(dev, struct_size(s, p, devtype->nr), GFP_KERNEL);
 	if (!s) {
 		dev_err(dev, "Error allocating port structure\n");
 		return -ENOMEM;
-- 
2.20.1