Message-ID: <20120910092954.10172gr8hhsdupc0@www.81.fi> (sfid-20120910_083002_299131_48559819)
Date: Mon, 10 Sep 2012 09:29:54 +0300
From: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
To: Wei Yongjun <weiyj.lk@gmail.com>
Cc: linville@tuxdriver.com, yongjun_wei@trendmicro.com.cn,
	linux-wireless@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH] rndis_wlan: move the dereference below the NULL test
References: <CAPgLHd97uPhcX-dTkur_Ceb=8YOwWQtbRk7MqirNvsYBbDoZ1A@mail.gmail.com>
In-Reply-To: <CAPgLHd97uPhcX-dTkur_Ceb=8YOwWQtbRk7MqirNvsYBbDoZ1A@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain;
 charset=ISO-8859-1;
 DelSp="Yes";
 format="flowed"
Sender: linux-wireless-owner@vger.kernel.org

Quoting Wei Yongjun <weiyj.lk@gmail.com>:

> From: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
>
> The dereference should be moved below the NULL test.
>
> spatch with a semantic match is used to found this.
> (http://coccinelle.lip6.fr/)
>
> Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
> ---
>  drivers/net/wireless/rndis_wlan.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/wireless/rndis_wlan.c  
> b/drivers/net/wireless/rndis_wlan.c
> index 7a4ae9e..de2a673 100644
> --- a/drivers/net/wireless/rndis_wlan.c
> +++ b/drivers/net/wireless/rndis_wlan.c
> @@ -1946,12 +1946,19 @@ static int rndis_get_tx_power(struct wiphy  
> *wiphy, int *dbm)
>  static int rndis_scan(struct wiphy *wiphy,
>  			struct cfg80211_scan_request *request)
>  {
> -	struct net_device *dev = request->wdev->netdev;
> -	struct usbnet *usbdev = netdev_priv(dev);
> -	struct rndis_wlan_private *priv = get_rndis_wlan_priv(usbdev);
> +	struct net_device *dev;
> +	struct usbnet *usbdev;
> +	struct rndis_wlan_private *priv;
>  	int ret;
>  	int delay = SCAN_DELAY_JIFFIES;
>
> +	if (!request)
> +		return -EINVAL;
> +
> +	dev = request->wdev->netdev;
> +	usbdev = netdev_priv(dev);
> +	priv = get_rndis_wlan_priv(usbdev);
> +

'request' is actually always valid pointer and the !request check is  
unneeded. Correct fix is to remove the check.

>  	netdev_dbg(usbdev->net, "cfg80211.scan\n");
>
>  	/* Get current bssid list from device before new scan, as new scan
> @@ -1959,9 +1966,6 @@ static int rndis_scan(struct wiphy *wiphy,
>  	 */
>  	rndis_check_bssid_list(usbdev, NULL, NULL);
>
> -	if (!request)
> -		return -EINVAL;
> -

Only this part is needed.

-Jussi

>  	if (priv->scan_request && priv->scan_request != request)
>  		return -EBUSY;
>