From: Pavel Emelyanov <xemul@openvz.org>
Date: Wed, 23 Apr 2008 07:47:15 +0000 (+0400)
Subject: mac80211: Fix race between ieee80211_rx_bss_put and lookup routines.
X-Git-Tag: v2.6.26-rc1~1088^2~4^2~7
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1ebebea8e844d01c80b93b8ee4d696ee7c0cbc27;p=linux-2.6

mac80211: Fix race between ieee80211_rx_bss_put and lookup routines.

The put routine first decrements the users counter and then
(if it is zero) locks the sta_bss_lock and removes one from
the list and the hash.

Thus, any of ieee80211_sta_config_auth, ieee80211_rx_bss_get
or ieee80211_rx_mesh_bss_get can race with it by finding a
bss that is about to get kfree-ed.

Using atomic_dec_and_lock in ieee80211_rx_bss_put takes care
of this race.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
---

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index c0a5345c8a..a5e5c31c23 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -2248,10 +2248,13 @@ static void ieee80211_rx_bss_put(struct net_device *dev,
 				 struct ieee80211_sta_bss *bss)
 {
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
-	if (!atomic_dec_and_test(&bss->users))
+
+	local_bh_disable();
+	if (!atomic_dec_and_lock(&bss->users, &local->sta_bss_lock)) {
+		local_bh_enable();
 		return;
+	}
 
-	spin_lock_bh(&local->sta_bss_lock);
 	__ieee80211_rx_bss_hash_del(dev, bss);
 	list_del(&bss->list);
 	spin_unlock_bh(&local->sta_bss_lock);