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Date:   Wed, 3 Apr 2019 11:40:52 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Amitkumar Karwar <amitkarwar@...il.com>,
        Nishant Sarmukadam <nishants@...vell.com>,
        Ganapathi Bhat <gbhat@...vell.com>,
        Xinming Hu <huxinming820@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH][next] mwifiex: use struct_size() in 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[];
};

size = sizeof(struct foo) + count * sizeof(struct boo);
instance = kzalloc(size, GFP_KERNEL)

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

instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL)

Notice that, in this case, variable regd_size is not necessary,
hence it is removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/net/wireless/marvell/mwifiex/sta_cmdresp.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/marvell/mwifiex/sta_cmdresp.c b/drivers/net/wireless/marvell/mwifiex/sta_cmdresp.c
index 69e3b624adbb..24b33e20e7a9 100644
--- a/drivers/net/wireless/marvell/mwifiex/sta_cmdresp.c
+++ b/drivers/net/wireless/marvell/mwifiex/sta_cmdresp.c
@@ -1025,17 +1025,14 @@ mwifiex_create_custom_regdomain(struct mwifiex_private *priv,
 	struct ieee80211_regdomain *regd;
 	struct ieee80211_reg_rule *rule;
 	bool new_rule;
-	int regd_size, idx, freq, prev_freq = 0;
+	int idx, freq, prev_freq = 0;
 	u32 bw, prev_bw = 0;
 	u8 chflags, prev_chflags = 0, valid_rules = 0;
 
 	if (WARN_ON_ONCE(num_chan > NL80211_MAX_SUPP_REG_RULES))
 		return ERR_PTR(-EINVAL);
 
-	regd_size = sizeof(struct ieee80211_regdomain) +
-		    num_chan * sizeof(struct ieee80211_reg_rule);
-
-	regd = kzalloc(regd_size, GFP_KERNEL);
+	regd = kzalloc(struct_size(regd, reg_rules, num_chan), GFP_KERNEL);
 	if (!regd)
 		return ERR_PTR(-ENOMEM);
 
-- 
2.21.0

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