From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S934287AbeAXQOy (ORCPT <rfc822;w@1wt.eu>);
        Wed, 24 Jan 2018 11:14:54 -0500
Received: from www381.your-server.de ([78.46.137.84]:37989 "EHLO
        www381.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S934021AbeAXQOx (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 24 Jan 2018 11:14:53 -0500
Subject: Re: [PATCH 1/2] regmap: fix NULL pointer dereference in
 regmap_name_read_file()
To: David Lechner <david@lechnology.com>, linux-kernel@vger.kernel.org
Cc: Mark Brown <broonie@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
References: <1516748023-17235-1-git-send-email-david@lechnology.com>
 <1516748023-17235-2-git-send-email-david@lechnology.com>
From: Lars-Peter Clausen <lars@metafoo.de>
Message-ID: <c7919cd8-447c-6eee-184a-0d40efbcbe75@metafoo.de>
Date: Wed, 24 Jan 2018 17:14:50 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.5.2
MIME-Version: 1.0
In-Reply-To: <1516748023-17235-2-git-send-email-david@lechnology.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
X-Authenticated-Sender: lars@metafoo.de
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 01/23/2018 11:53 PM, David Lechner wrote:
> This fixes a possible NULL pointer dereference oops in
> regmap_name_read_file() when the regmap does not have a device
> associated with it.
> 
> Signed-off-by: David Lechner <david@lechnology.com>
> ---
>  drivers/base/regmap/regmap-debugfs.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
> index 36ce351..0df7379 100644
> --- a/drivers/base/regmap/regmap-debugfs.c
> +++ b/drivers/base/regmap/regmap-debugfs.c
> @@ -40,6 +40,7 @@ static ssize_t regmap_name_read_file(struct file *file,
>  				     loff_t *ppos)
>  {
>  	struct regmap *map = file->private_data;
> +	const char *name = NULL;
>  	int ret;
>  	char *buf;
>  
> @@ -47,7 +48,10 @@ static ssize_t regmap_name_read_file(struct file *file,
>  	if (!buf)
>  		return -ENOMEM;
>  
> -	ret = snprintf(buf, PAGE_SIZE, "%s\n", map->dev->driver->name);
> +	if (map->dev && map->dev->driver)
> +		name = map->dev->driver->name;
> +
> +	ret = snprintf(buf, PAGE_SIZE, "%s\n", name);

Won't this print "(null)" now? Not sure if that is the best approach.