linux-kernel - [PATCH] drivers: qcom: rpmh: use struct

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Message-ID: <20180824011753.GA25826@embeddedor.com>
Date:   Thu, 23 Aug 2018 20:17:53 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] drivers: qcom: rpmh: 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;
        void *entry[];
};

instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_ATOMIC);

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_ATOMIC);

This issue was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/soc/qcom/rpmh.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
index c7beb68..12c057a 100644
--- a/drivers/soc/qcom/rpmh.c
+++ b/drivers/soc/qcom/rpmh.c
@@ -362,8 +362,7 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
 	if (!count)
 		return -EINVAL;
 
-	req = kzalloc(sizeof(*req) + count * sizeof(req->rpm_msgs[0]),
-		      GFP_ATOMIC);
+	req = kzalloc(struct_size(req, rpm_msgs, count), GFP_ATOMIC);
 	if (!req)
 		return -ENOMEM;
 	req->count = count;
-- 
2.7.4