linux-kernel - [PATCH] hpet: Use struct

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Date:   Tue, 19 Feb 2019 16:10:54 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Clemens Ladisch <clemens@...isch.de>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] hpet: 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 siz 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/char/hpet.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c
index 9bffcd37cc7b..d0ad85900b79 100644
--- a/drivers/char/hpet.c
+++ b/drivers/char/hpet.c
@@ -842,7 +842,6 @@ int hpet_alloc(struct hpet_data *hdp)
 	struct hpet_dev *devp;
 	u32 i, ntimer;
 	struct hpets *hpetp;
-	size_t siz;
 	struct hpet __iomem *hpet;
 	static struct hpets *last;
 	unsigned long period;
@@ -860,10 +859,8 @@ int hpet_alloc(struct hpet_data *hdp)
 		return 0;
 	}
 
-	siz = sizeof(struct hpets) + ((hdp->hd_nirqs - 1) *
-				      sizeof(struct hpet_dev));
-
-	hpetp = kzalloc(siz, GFP_KERNEL);
+	hpetp = kzalloc(struct_size(hpetp, hp_dev, hdp->hd_nirqs - 1),
+			GFP_KERNEL);
 
 	if (!hpetp)
 		return -ENOMEM;
-- 
2.20.1