linux-kernel - Re: [PATCH] staging: pi433: fix potential null dereference

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Message-ID: <20181126094745.GF3088@unbuntlaptop>
Date:   Mon, 26 Nov 2018 12:47:45 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Michael Straube <straube.linux@...il.com>
Cc:     gregkh@...uxfoundation.org, devel@...verdev.osuosl.org,
        linux@...f-entwicklungen.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: pi433: fix potential null dereference

On Sun, Nov 25, 2018 at 10:22:25AM +0100, Michael Straube wrote:
> Add a test for successful call to cdev_alloc() to avoid
> potential null dereference. Issue reported by smatch.
> 

Fixes: 874bcba65f9a ("staging: pi433: New driver")


> Signed-off-by: Michael Straube <straube.linux@...il.com>
> ---
>  drivers/staging/pi433/pi433_if.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/staging/pi433/pi433_if.c b/drivers/staging/pi433/pi433_if.c
> index 786478671190..d72de2105053 100644
> --- a/drivers/staging/pi433/pi433_if.c
> +++ b/drivers/staging/pi433/pi433_if.c
> @@ -1245,6 +1245,10 @@ static int pi433_probe(struct spi_device *spi)
>  
>  	/* create cdev */
>  	device->cdev = cdev_alloc();
> +	if (!device->cdev) {
> +		dev_dbg(device->dev, "allocation of cdev failed");
> +		goto cdev_failed;
> +	}
>  	device->cdev->owner = THIS_MODULE;
>  	cdev_init(device->cdev, &pi433_fops);
>  	retval = cdev_add(device->cdev, device->devt, 1);

There is a second related bug here if we cdev_add() fails then we should
call cdev_del(device->cdev).  (cdev_del() does not take a NULL cdev
pointer).

regards,
dan carpenter