mac80211: fix IBSS teardown race

commit f3209bea110cade12e2b133da8b8499689cb0e2e upstream.

Ignacy reports that sometimes after leaving an IBSS
joining a new one didn't work because there still
were stations on the list. He fixed it by flushing
stations when attempting to join a new IBSS, but
this shouldn't be happening in the first case. When
I looked into it I saw a race condition in teardown
that could cause stations to be added after flush,
and thus cause this situation. Ignacy confirms that
after applying my patch he hasn't seen this happen
again.

Reported-by: Ignacy Gawedzki <i@lri.fr>
Debugged-by: Ignacy Gawedzki <i@lri.fr>
Tested-by: Ignacy Gawedzki <i@lri.fr>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
index 3e81af1fce58177da28120b47111283c443fad99..821590df576f6e04f36dcaea0d3e82e0ee0ae905 100644 (file)
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -967,6 +967,10 @@ int ieee80211_ibss_leave(struct ieee80211_sub_if_data *sdata)
 
        mutex_lock(&sdata->u.ibss.mtx);
 
+       sdata->u.ibss.state = IEEE80211_IBSS_MLME_SEARCH;
+       memset(sdata->u.ibss.bssid, 0, ETH_ALEN);
+       sdata->u.ibss.ssid_len = 0;
+
        active_ibss = ieee80211_sta_active_ibss(sdata);
 
        if (!active_ibss && !is_zero_ether_addr(ifibss->bssid)) {
@@ -1000,8 +1004,6 @@ int ieee80211_ibss_leave(struct ieee80211_sub_if_data *sdata)
        kfree_skb(skb);
 
        skb_queue_purge(&sdata->skb_queue);
-       memset(sdata->u.ibss.bssid, 0, ETH_ALEN);
-       sdata->u.ibss.ssid_len = 0;
 
        del_timer_sync(&sdata->u.ibss.timer);