linux-kernel - [PATCH] drm/sun4i: tcon-top: Use struct_size() in devm

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Date:   Thu, 23 Aug 2018 20:05:21 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Maxime Ripard <maxime.ripard@...tlin.com>,
        David Airlie <airlied@...ux.ie>, Chen-Yu Tsai <wens@...e.org>
Cc:     dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] drm/sun4i: tcon-top: 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;
        void *entry[];
};

instance = devm_kzalloc(dev, 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 = devm_kzalloc(dev, struct_size(instance, entry, count), GFP_KERNEL);

This issue was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/gpu/drm/sun4i/sun8i_tcon_top.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun8i_tcon_top.c b/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
index 55fe398..3040a79 100644
--- a/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
+++ b/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
@@ -129,8 +129,7 @@ static int sun8i_tcon_top_bind(struct device *dev, struct device *master,
 	if (!tcon_top)
 		return -ENOMEM;
 
-	clk_data = devm_kzalloc(dev, sizeof(*clk_data) +
-				sizeof(*clk_data->hws) * CLK_NUM,
+	clk_data = devm_kzalloc(dev, struct_size(clk_data, hws, CLK_NUM),
 				GFP_KERNEL);
 	if (!clk_data)
 		return -ENOMEM;
-- 
2.7.4