Re: [PATCH v2 1/6] staging: rtl8188eu: use safe iterator in rtw_free_network_queue

Guenter Roeck
2021-05-17T20:30:22Z

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@kaiser.cx>

Reviewed-by: Guenter Roeck <linux@roeck-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
>