Commit 1ebebea8 authored Apr 23, 2008 by Pavel Emelyanov Committed by John W. Linville Apr 23, 2008

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>

parent d1d8f44a

net/mac80211/mlme.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -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);

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