linux-kernel - Re: [PATCH] input: synaptics-rmi4: check for null rmi

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Date:   Tue, 20 Dec 2016 13:22:59 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Andrew Duggan <aduggan@...aptics.com>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Lyude Paul <thatslyude@...il.com>,
        Dennis Wassenberg <dennis.wassenberg@...unet.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] input: synaptics-rmi4: check for null rmi_dev before it
 is dereferenced

Hi Colin,

On Tue, Dec 20, 2016 at 10:07:50AM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> rmi_dev is currently being dereferenced before it null checked, so we
> have a potential null pointer dereference issue with this.  Fix this
> by dereferencing rmi_dev after a null check has been performed.
> 
> Fixes CoverityScan CID 1391218 ("Dereference before null check")

I'd rather we removed the NULL check instead. As far as I can see it
can't even be NULL.

> 
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/input/rmi4/rmi_f03.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/input/rmi4/rmi_f03.c b/drivers/input/rmi4/rmi_f03.c
> index 8a7ca3e..008f42a 100644
> --- a/drivers/input/rmi4/rmi_f03.c
> +++ b/drivers/input/rmi4/rmi_f03.c
> @@ -164,7 +164,7 @@ static int rmi_f03_config(struct rmi_function *fn)
>  static int rmi_f03_attention(struct rmi_function *fn, unsigned long *irq_bits)
>  {
>  	struct rmi_device *rmi_dev = fn->rmi_dev;
> -	struct rmi_driver_data *drvdata = dev_get_drvdata(&rmi_dev->dev);
> +	struct rmi_driver_data *drvdata;
>  	struct f03_data *f03 = dev_get_drvdata(&fn->dev);
>  	u16 data_addr = fn->fd.data_base_addr;
>  	const u8 ob_len = f03->rx_queue_length * RMI_F03_OB_SIZE;
> @@ -178,6 +178,7 @@ static int rmi_f03_attention(struct rmi_function *fn, unsigned long *irq_bits)
>  	if (!rmi_dev)
>  		return -ENODEV;
>  
> +	drvdata = dev_get_drvdata(&rmi_dev->dev);
>  	if (drvdata->attn_data.data) {
>  		/* First grab the data passed by the transport device */
>  		if (drvdata->attn_data.size < ob_len) {
> -- 
> 2.10.2
> 

Thanks.

-- 
Dmitry