[PATCH] udlfb: fix some inconsistent NULL checking

[Bartlomiej Zolnierkiewicz]

[ added Mikulas, Alexey, Colin & Wen to Cc: ]

On 10/10/2018 12:36 PM, Dan Carpenter wrote:
> In the current kernel, then kzalloc() can't fail for small allocations,
> but if it did fail then we would have a NULL dereference in the error
> handling.  Also in dlfb_usb_disconnect() if "info" were NULL then it
> would cause an Oops inside the unregister_framebuffer() function but it
> can't be NULL so let's remove that check.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>

Patch queued for 4.21, thanks (also sorry for the delay).

[ Mikulas, Alexey, Colin & Wen: please verify that there are no known
  issues with udlfb left with this patch applied (thanks!). ]

> diff --git a/drivers/video/fbdev/udlfb.c b/drivers/video/fbdev/udlfb.c
> index 070026a7e55a..1d034dddc556 100644
> --- a/drivers/video/fbdev/udlfb.c
> +++ b/drivers/video/fbdev/udlfb.c
> @@ -1598,7 +1598,7 @@ static int dlfb_usb_probe(struct usb_interface *intf,
>  	dlfb = kzalloc(sizeof(*dlfb), GFP_KERNEL);
>  	if (!dlfb) {
>  		dev_err(&intf->dev, "%s: failed to allocate dlfb\n", __func__);
> -		goto error;
> +		return -ENOMEM;
>  	}
>  
>  	INIT_LIST_HEAD(&dlfb->deferred_free);
> @@ -1703,7 +1703,7 @@ static int dlfb_usb_probe(struct usb_interface *intf,
>  error:
>  	if (dlfb->info) {
>  		dlfb_ops_destroy(dlfb->info);
> -	} else if (dlfb) {
> +	} else {
>  		usb_put_dev(dlfb->udev);
>  		kfree(dlfb);
>  	}
> @@ -1730,12 +1730,10 @@ static void dlfb_usb_disconnect(struct usb_interface *intf)
>  	/* this function will wait for all in-flight urbs to complete */
>  	dlfb_free_urb_list(dlfb);
>  
> -	if (info) {
> -		/* remove udlfb's sysfs interfaces */
> -		for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++)
> -			device_remove_file(info->dev, &fb_device_attrs[i]);
> -		device_remove_bin_file(info->dev, &edid_attr);
> -	}
> +	/* remove udlfb's sysfs interfaces */
> +	for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++)
> +		device_remove_file(info->dev, &fb_device_attrs[i]);
> +	device_remove_bin_file(info->dev, &edid_attr);
>  
>  	unregister_framebuffer(info);
>  }

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics