linux-kernel - Re: [PATCH v2] mtd: rawnand: atmel: Fix potential NULL pointer dereference

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Message-ID: <20180918155849.178c5f48@bbrezillon>
Date:   Tue, 18 Sep 2018 15:58:49 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        linux-mtd@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mtd: rawnand: atmel: Fix potential NULL pointer
 dereference

On Tue, 18 Sep 2018 08:55:55 -0500
"Gustavo A. R. Silva" <gustavo@...eddedor.com> wrote:

> There is a potential execution path in which function
> of_find_compatible_node() returns NULL. In such a case,
> we end up having a NULL pointer dereference when accessing
> pointer *nfc_np* in function of_clk_get().
> 
> So, we better don't take any chances and fix this by null
> checking pointer *nfc_np* before calling of_clk_get().
> 
> Addresses-Coverity-ID: 1473052 ("Dereference null return value")
> Fixes: f88fc122cc34 ("mtd: nand: Cleanup/rework the atmel_nand driver")
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

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

> ---
> Changes in v2:
>  - Add Fixes tag to the commit log.
>  - Remove blank line before null checking nfc_np.
> 
>  drivers/mtd/nand/raw/atmel/nand-controller.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/mtd/nand/raw/atmel/nand-controller.c b/drivers/mtd/nand/raw/atmel/nand-controller.c
> index a38633a..5bfbe97 100644
> --- a/drivers/mtd/nand/raw/atmel/nand-controller.c
> +++ b/drivers/mtd/nand/raw/atmel/nand-controller.c
> @@ -2034,6 +2034,10 @@ atmel_hsmc_nand_controller_legacy_init(struct atmel_hsmc_nand_controller *nc)
>  	nand_np = dev->of_node;
>  	nfc_np = of_find_compatible_node(dev->of_node, NULL,
>  					 "atmel,sama5d3-nfc");
> +	if (!nfc_np) {
> +		dev_err(dev, "Could not find device node for sama5d3-nfc\n");
> +		return -ENODEV;
> +	}
>  
>  	nc->clk = of_clk_get(nfc_np, 0);
>  	if (IS_ERR(nc->clk)) {