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Date:   Tue, 8 Jan 2019 09:52:44 -0600
From:   "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To:     David Woodhouse <dwmw2@infradead.org>,
        Brian Norris <computersforpeace@gmail.com>,
        Boris Brezillon <bbrezillon@kernel.org>,
        Marek Vasut <marek.vasut@gmail.com>,
        Richard Weinberger <richard@nod.at>
Cc:     linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
        "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH] mtd: cfi: cmdset_0001: Use struct_size() in kmalloc()
Message-ID: <20190108155244.GA15339@embeddedor>
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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 = kmalloc(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 = kmalloc(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/mtd/chips/cfi_cmdset_0001.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/chips/cfi_cmdset_0001.c b/drivers/mtd/chips/cfi_cmdset_0001.c
index 6e8e7b1bb34b..79a53cb8507b 100644
--- a/drivers/mtd/chips/cfi_cmdset_0001.c
+++ b/drivers/mtd/chips/cfi_cmdset_0001.c
@@ -756,7 +756,8 @@ static int cfi_intelext_partition_fixup(struct mtd_info *mtd,
 		}
 
 		numvirtchips = cfi->numchips * numparts;
-		newcfi = kmalloc(sizeof(struct cfi_private) + numvirtchips * sizeof(struct flchip), GFP_KERNEL);
+		newcfi = kmalloc(struct_size(newcfi, chips, numvirtchips),
+				 GFP_KERNEL);
 		if (!newcfi)
 			return -ENOMEM;
 		shared = kmalloc_array(cfi->numchips,
-- 
2.20.1