linux-kernel - Re: [PATCH v2 1/6] staging: rtl8188eu: use safe iterator in rtw_free_network

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Date:   Mon, 17 May 2021 13:30:16 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Martin Kaiser <martin@...ser.cx>
Cc:     Larry Finger <Larry.Finger@...inger.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        linux-staging@...ts.linux.dev, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/6] staging: rtl8188eu: use safe iterator in
 rtw_free_network_queue

On Mon, May 17, 2021 at 10:18:21PM +0200, Martin Kaiser wrote:
> rtw_free_network_queue iterates over the scanned wireless networks and
> calls _rtw_free_network for each of them. In some cases,
> _rtw_free_network removes a network from the list.
> 
> We have to use list_for_each_entry_safe if we remove list entries while
> we iterate over a list.
> 
> Fixes: 23017c8842d2 ("staging: rtl8188eu: Use list iterators and helpers")
> Signed-off-by: Martin Kaiser <martin@...ser.cx>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
> v2:
>  - use list_for_each_entry_safe
> 
> Without this patch, it's easy to get the driver into an endless loop by
> scanning, connecting and disconnecting repeatedly.
> 
> wpa_supplicant -B -Dwext -i wlan0 -c /path/to/my/config...
> while true ; do
>    sleep 1
>    wpa_cli reconfigure
>    wpa_cli add_network
>    wpa_cli set_network 0 ssid ...
>    wpa_cli set_network 0 psk ...
>    wpa_cli select_network 0
>    sleep 6
>    wpa_cli status
>    wpa_cli disconnect 0
> done
> 
>  drivers/staging/rtl8188eu/core/rtw_mlme.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/staging/rtl8188eu/core/rtw_mlme.c b/drivers/staging/rtl8188eu/core/rtw_mlme.c
> index 159465b073c2..ba73ac5325e2 100644
> --- a/drivers/staging/rtl8188eu/core/rtw_mlme.c
> +++ b/drivers/staging/rtl8188eu/core/rtw_mlme.c
> @@ -199,19 +199,17 @@ struct wlan_network *rtw_find_network(struct __queue *scanned_queue, u8 *addr)
>  
>  void rtw_free_network_queue(struct adapter *padapter, u8 isfreeall)
>  {
> -	struct list_head *phead, *plist;
> -	struct wlan_network *pnetwork;
> +	struct list_head *phead;
> +	struct wlan_network *pnetwork, *temp;
>  	struct mlme_priv *pmlmepriv = &padapter->mlmepriv;
>  	struct __queue *scanned_queue = &pmlmepriv->scanned_queue;
>  
>  	spin_lock_bh(&scanned_queue->lock);
>  
>  	phead = get_list_head(scanned_queue);
> -	list_for_each(plist, phead) {
> -		pnetwork = list_entry(plist, struct wlan_network, list);
> -
> +	list_for_each_entry_safe(pnetwork, temp, phead, list)
>  		_rtw_free_network(pmlmepriv, pnetwork, isfreeall);
> -	}
> +
>  	spin_unlock_bh(&scanned_queue->lock);
>  }
>  
> -- 
> 2.20.1
>