linux-kernel - [PATCH net-next] net: hns: Use struct_size() in devm

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Message-ID: <20190116010456.GA29582@embeddedor>
Date:   Tue, 15 Jan 2019 19:04:56 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Yisen Zhuang <yisen.zhuang@...wei.com>,
        Salil Mehta <salil.mehta@...wei.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH net-next] net: hns: 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;
    struct boo entry[];
};

instance = devm_kzalloc(dev, sizeof(struct foo) + count * sizeof(struct boo), 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/net/ethernet/hisilicon/hns/hns_dsaf_rcb.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hns/hns_dsaf_rcb.c b/drivers/net/ethernet/hisilicon/hns/hns_dsaf_rcb.c
index 5d64519b9b1d..6bf346c11b25 100644
--- a/drivers/net/ethernet/hisilicon/hns/hns_dsaf_rcb.c
+++ b/drivers/net/ethernet/hisilicon/hns/hns_dsaf_rcb.c
@@ -788,8 +788,9 @@ int hns_rcb_common_get_cfg(struct dsaf_device *dsaf_dev,
 	int ring_num = hns_rcb_get_ring_num(dsaf_dev);
 
 	rcb_common =
-		devm_kzalloc(dsaf_dev->dev, sizeof(*rcb_common) +
-			ring_num * sizeof(struct ring_pair_cb), GFP_KERNEL);
+		devm_kzalloc(dsaf_dev->dev,
+			     struct_size(rcb_common, ring_pair_cb, ring_num),
+			     GFP_KERNEL);
 	if (!rcb_common) {
 		dev_err(dsaf_dev->dev, "rcb common devm_kzalloc fail!\n");
 		return -ENOMEM;
-- 
2.20.1