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Date:   Tue, 8 Jan 2019 11:26:32 -0600
From:   "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To:     Igor Mitsyanko <imitsyanko@quantenna.com>,
        Avinash Patil <avinashp@quantenna.com>,
        Sergey Matyukevich <smatyukevich@quantenna.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        "David S. Miller" <davem@davemloft.net>
Cc:     linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH] qtnfmac: use struct_size() in kzalloc()
Message-ID: <20190108172632.GA2918@embeddedor>
MIME-Version: 1.0
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User-Agent: Mutt/1.9.4 (2018-02-28)
Sender: linux-kernel-owner@vger.kernel.org
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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 = kzalloc(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 = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/net/wireless/quantenna/qtnfmac/commands.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/quantenna/qtnfmac/commands.c b/drivers/net/wireless/quantenna/qtnfmac/commands.c
index 659e7649fe22..cf386f579060 100644
--- a/drivers/net/wireless/quantenna/qtnfmac/commands.c
+++ b/drivers/net/wireless/quantenna/qtnfmac/commands.c
@@ -914,9 +914,8 @@ qtnf_cmd_resp_proc_hw_info(struct qtnf_bus *bus,
 	if (WARN_ON(resp->n_reg_rules > NL80211_MAX_SUPP_REG_RULES))
 		return -E2BIG;
 
-	hwinfo->rd = kzalloc(sizeof(*hwinfo->rd)
-			     + sizeof(struct ieee80211_reg_rule)
-			     * resp->n_reg_rules, GFP_KERNEL);
+	hwinfo->rd = kzalloc(struct_size(hwinfo->rd, reg_rules,
+					 resp->n_reg_rules), GFP_KERNEL);
 
 	if (!hwinfo->rd)
 		return -ENOMEM;
-- 
2.20.1