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

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Message-Id: <20210517201826.25150-1-martin@kaiser.cx>
Date:   Mon, 17 May 2021 22:18:21 +0200
From:   Martin Kaiser <martin@...ser.cx>
To:     Larry Finger <Larry.Finger@...inger.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Dan Carpenter <dan.carpenter@...cle.com>
Cc:     linux-staging@...ts.linux.dev, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org, Martin Kaiser <martin@...ser.cx>
Subject: [PATCH v2 1/6] staging: rtl8188eu: use safe iterator in rtw_free_network_queue

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>
---
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