linux-kernel - [PATCH net-next] can: kvaser_usb: Use struct_size() in alloc

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Message-ID: <20190208031035.GA2665@embeddedor>
Date:   Thu, 7 Feb 2019 21:10:35 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>
Cc:     linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH net-next] can: kvaser_usb: Use struct_size() in alloc_candev()

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 = alloc(sizeof(struct foo) + count * sizeof(void *));

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

instance = alloc(struct_size(instance, entry, count));

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c b/drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c
index c89c7d4900d7..0f1d3e807d63 100644
--- a/drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c
+++ b/drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c
@@ -643,8 +643,7 @@ static int kvaser_usb_init_one(struct kvaser_usb *dev,
 			return err;
 	}
 
-	netdev = alloc_candev(sizeof(*priv) +
-			      dev->max_tx_urbs * sizeof(*priv->tx_contexts),
+	netdev = alloc_candev(struct_size(priv, tx_contexts, dev->max_tx_urbs),
 			      dev->max_tx_urbs);
 	if (!netdev) {
 		dev_err(&dev->intf->dev, "Cannot alloc candev\n");
-- 
2.20.1