net: usb: cdc-phonet: use struct_size() in alloc_netdev()

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.

---
 drivers/net/usb/cdc-phonet.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index 78b16eb9e58c..63aaae487995 100644
@@ -361,8 +361,8 @@ static int usbpn_probe(struct usb_interface *intf, const struct usb_device_id *i
 	else
 		return -EINVAL;
 
-	dev = alloc_netdev(sizeof(*pnd) + sizeof(pnd->urbs[0]) * rxq_size,
-			   ifname, NET_NAME_UNKNOWN, usbpn_setup);
+	dev = alloc_netdev(struct_size(pnd, urbs, rxq_size), ifname,
+			   NET_NAME_UNKNOWN, usbpn_setup);
 	if (!dev)
 		return -ENOMEM;
 

From: "Gustavo A. R. Silva" <[email protected]>
Date: Thu, 7 Feb 2019 21:13:13 -0600

Applied.