linux-kernel - Re: [PATCH] mtd: nand: sunxi: fix potential divide-by-zero error

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Date:   Mon, 31 Jul 2017 18:28:40 +0200
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Bryan O'Donoghue <pure.logic@...us-software.ie>
Cc:     richard@....at, dwmw2@...radead.org, computersforpeace@...il.com,
        marek.vasut@...il.com, cyrille.pitchen@...ev4u.fr,
        maxime.ripard@...e-electrons.com, wens@...e.org,
        linux-mtd@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: nand: sunxi: fix potential divide-by-zero error

On Fri, 28 Jul 2017 14:22:57 +0100
Bryan O'Donoghue <pure.logic@...us-software.ie> wrote:

> clk_round_rate() can return <= 0. Currently the value returned by
> clk_round_rate() is used directly for a division. This patch introduces a
> guard to ensure a divide-by-zero or a divide by a negative number for that
> matter can't happen by bugging out returning -EINVAL if clk_round_rate()
> returns <= 0.

Applied to nand/fixes.

Thanks,

Boris

> 
> Fixes: 2d43457f79e4 ("mtd: nand: sunxi: fix EDO mode selection")
> 
> Signed-off-by: Bryan O'Donoghue <pure.logic@...us-software.ie>
> ---
>  drivers/mtd/nand/sunxi_nand.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
> index d0b6f8f..6abd142 100644
> --- a/drivers/mtd/nand/sunxi_nand.c
> +++ b/drivers/mtd/nand/sunxi_nand.c
> @@ -1728,6 +1728,10 @@ static int sunxi_nfc_setup_data_interface(struct mtd_info *mtd, int csline,
>  	 */
>  	chip->clk_rate = NSEC_PER_SEC / min_clk_period;
>  	real_clk_rate = clk_round_rate(nfc->mod_clk, chip->clk_rate);
> +	if (real_clk_rate <= 0) {
> +		dev_err(nfc->dev, "Unable to round clk %lu\n", chip->clk_rate);
> +		return -EINVAL;
> +	}
>  
>  	/*
>  	 * ONFI specification 3.1, paragraph 4.15.2 dictates that EDO data