linux-kernel - Re: [v1] i2c: busses: i2c-designware-pcidrv:- Handle return NULL error from pcim_iomap

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Date:   Thu, 22 Dec 2016 13:50:33 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Arvind Yadav <arvind.yadav.cs@...il.com>
Cc:     jarkko.nikula@...ux.intel.com, wsa@...-dreams.de,
        andriy.shevchenko@...ux.intel.com, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [v1] i2c: busses: i2c-designware-pcidrv:- Handle return NULL
 error from pcim_iomap_table

On Thu, Dec 22, 2016 at 05:09:19PM +0530, Arvind Yadav wrote:
> Here, If pcim_iomap_table will fail. It will return NULL.
> Kernel can run into a NULL-pointer dereference.
> This error check will avoid NULL pointer dereference.
> 
> Signed-off-by: Arvind Yadav <arvind.yadav.cs@...il.com>
> ---
>  drivers/i2c/busses/i2c-designware-pcidrv.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-designware-pcidrv.c b/drivers/i2c/busses/i2c-designware-pcidrv.c
> index d6423cf..6a1907d 100644
> --- a/drivers/i2c/busses/i2c-designware-pcidrv.c
> +++ b/drivers/i2c/busses/i2c-designware-pcidrv.c
> @@ -235,6 +235,10 @@ static int i2c_dw_pci_probe(struct pci_dev *pdev,
>  	dev->controller = controller;
>  	dev->get_clk_rate_khz = i2c_dw_get_clk_rate_khz;
>  	dev->base = pcim_iomap_table(pdev)[0];
> +	if (!dev->base) {
> +		dev_err(&pdev->dev, "I/O map table allocation failed\n");
> +		return -ENOMEM;

Are you sure this can actually happen?

IIRC pcim_iomap_regions() (which is called before this) makes sure the
BARs you access here are valid.