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mac80211: Fix race between ieee80211_rx_bss_put and lookup routines.

PATCH In review Pavel Emelyanov 2 participants 2 messages Apr 23, 2008 1 message not in the archive

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Networking Network drivers mac80211
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Pavel Emelyanov

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#0 lore raw

PATCH 1/1 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 <[email protected]>

---

net/mac80211/mlme.c +5 -2
index 6b75cb6..dac3c2a 100644
@@ -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);

A message that is not in the archive (sent off-list or not yet received): [email protected]

Acked-by
#2 lore raw
Quoted 10 lines · Pavel Emelyanov

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.

Good catch, thanks.

Quoted 1 line
Signed-off-by Pavel Emelyanov <[email protected]>
Acked-by Johannes Berg <[email protected]>

I think we will need this in -stable (different file, same contents)

Quoted 23 lines

---

net/mac80211/mlme.c +5 -2
index 6b75cb6..dac3c2a 100644
@@ -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);