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

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Date:   Mon, 17 May 2021 22:21:54 +0200
From:   Martin Kaiser <martin@...ser.cx>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     Larry Finger <Larry.Finger@...inger.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        linux-staging@...ts.linux.dev, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] staging: rtl8188eu: use safe iterator in
 rtw_free_network_queue

Thus wrote Christophe JAILLET (christophe.jaillet@...adoo.fr):

> Le 16/05/2021 à 18:06, Martin Kaiser a écrit :
> > 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_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>
> > ---
> > 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 | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)

> > diff --git a/drivers/staging/rtl8188eu/core/rtw_mlme.c b/drivers/staging/rtl8188eu/core/rtw_mlme.c
> > index 159465b073c2..14816ad51668 100644
> > --- a/drivers/staging/rtl8188eu/core/rtw_mlme.c
> > +++ b/drivers/staging/rtl8188eu/core/rtw_mlme.c
> > @@ -199,7 +199,7 @@ 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 list_head *phead, *plist, *temp;
> >   	struct wlan_network *pnetwork;
> >   	struct mlme_priv *pmlmepriv = &padapter->mlmepriv;
> >   	struct __queue *scanned_queue = &pmlmepriv->scanned_queue;
> > @@ -207,7 +207,7 @@ void rtw_free_network_queue(struct adapter *padapter, u8 isfreeall)
> >   	spin_lock_bh(&scanned_queue->lock);
> >   	phead = get_list_head(scanned_queue);
> > -	list_for_each(plist, phead) {
> > +	list_for_each_safe(plist, temp, phead) {
> >   		pnetwork = list_entry(plist, struct wlan_network, list);
> >   		_rtw_free_network(pmlmepriv, pnetwork, isfreeall);

> Nitpicking: 'list_for_each_entry_safe' could also be used to simplify code.

Thanks for the hint, I just sent out v2.