linux-kernel - Re: [PATCH] mtd: nand: mxc_nand: fix a possible NULL dereference

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Date:	Thu, 12 Nov 2015 09:19:09 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	LABBE Corentin <clabbe.montjoie@...il.com>
Cc:	baruch@...s.co.il, computersforpeace@...il.com,
	dwmw2@...radead.org, fransklaver@...il.com,
	k.kozlowski.k@...il.com, luis@...ethencourt.com,
	s.hauer@...gutronix.de, linux-kernel@...r.kernel.org,
	linux-mtd@...ts.infradead.org
Subject: Re: [PATCH] mtd: nand: mxc_nand: fix a possible NULL dereference

Hello Corentin,

On Thu, Nov 12, 2015 at 08:46:55AM +0100, LABBE Corentin wrote:
> of_match_device could return NULL, and so cause a NULL pointer
> dereference later.
> 
> Signed-off-by: LABBE Corentin <clabbe.montjoie@...il.com>
> ---
>  drivers/mtd/nand/mxc_nand.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c
> index 136e73a..9e42431 100644
> --- a/drivers/mtd/nand/mxc_nand.c
> +++ b/drivers/mtd/nand/mxc_nand.c
> @@ -1464,8 +1464,7 @@ static int __init mxcnd_probe_dt(struct mxc_nand_host *host)
>  {
>  	struct device_node *np = host->dev->of_node;
>  	struct mxc_nand_platform_data *pdata = &host->pdata;
> -	const struct of_device_id *of_id =
> -		of_match_device(mxcnd_dt_ids, host->dev);
> +	const struct of_device_id *of_id;
>  	int buswidth;
>  
>  	if (!np)
> @@ -1482,6 +1481,9 @@ static int __init mxcnd_probe_dt(struct mxc_nand_host *host)
>  
>  	pdata->width = buswidth / 8;
>  
> +	of_id = of_match_device(mxcnd_dt_ids, host->dev);
> +	if (!of_id)
> +		return -ENODEV;

You should return 1 here instead of -ENODEV. Also this check should
better be done instead of

	if (!np)
		return 1;

at the start of the function. I really wonder there is no helper
function like:

	#define of_sensible_name(dev)	of_match_device(dev->driver->of_match_table, dev)

Best regards
Uwe

>  	host->devtype_data = of_id->data;
>  
>  	return 0;
> -- 
> 2.4.10
> 
> 

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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