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Date:   Thu, 23 Aug 2018 23:27:47 +0200
From:   Boris Brezillon <boris.brezillon@bootlin.com>
To:     "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Cc:     Harvey Hunt <harveyhuntnexus@gmail.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        David Woodhouse <dwmw2@infradead.org>,
        Brian Norris <computersforpeace@gmail.com>,
        Marek Vasut <marek.vasut@gmail.com>,
        linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
        Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH] mtd: rawnand: jz4780: use struct_size() in
 devm_kzalloc()
Message-ID: <20180823232747.072af43d@bbrezillon>
In-Reply-To: <20180823193332.GA31602@embeddedor.com>
References: <20180823193332.GA31602@embeddedor.com>
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On Thu, 23 Aug 2018 14:33:32 -0500
"Gustavo A. R. Silva" <gustavo@embeddedor.com> wrote:

> 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);

Oh, I didn't know about that one. That's nice!

> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>

> ---
>  drivers/mtd/nand/raw/jz4780_nand.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/raw/jz4780_nand.c b/drivers/mtd/nand/raw/jz4780_nand.c
> index db4fa60..ac62395 100644
> --- a/drivers/mtd/nand/raw/jz4780_nand.c
> +++ b/drivers/mtd/nand/raw/jz4780_nand.c
> @@ -352,7 +352,7 @@ static int jz4780_nand_probe(struct platform_device *pdev)
>  		return -ENODEV;
>  	}
>  
> -	nfc = devm_kzalloc(dev, sizeof(*nfc) + (sizeof(nfc->cs[0]) * num_banks), GFP_KERNEL);
> +	nfc = devm_kzalloc(dev, struct_size(nfc, cs, num_banks), GFP_KERNEL);
>  	if (!nfc)
>  		return -ENOMEM;
>