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

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Date:   Sun, 16 May 2021 18:06:08 +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>
Cc:     linux-staging@...ts.linux.dev, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org, Martin Kaiser <martin@...ser.cx>
Subject: [PATCH 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_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);
-- 
2.20.1