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

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Date:	Thu, 12 Nov 2015 09:03:11 +0100
From:	Frans Klaver <fransklaver@...il.com>
To:	LABBE Corentin <clabbe.montjoie@...il.com>
Cc:	baruch@...s.co.il, Brian Norris <computersforpeace@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Krzysztof Kozłowski <k.kozlowski.k@...il.com>,
	Luis de Bethencourt <luis@...ethencourt.com>,
	s.hauer@...gutronix.de, u.kleine-koenig@...gutronix.de,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mtd@...ts.infradead.org
Subject: Re: [PATCH] mtd: nand: mxc_nand: fix a possible NULL dereference

Hi,

On Thu, Nov 12, 2015 at 8:46 AM, LABBE Corentin
<clabbe.montjoie@...il.com> wrote:
> of_match_device could return NULL, and so cause a NULL pointer
> dereference later.

Did you actually run into this? It seems to me that this driver is
only probed if and only if we have a match and that therefore
of_match_device will always return a valid pointer (it is using the
same match table). Am I missing something?


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

Thanks,
Frans
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