Commit 53918994 authored by Johannes Berg's avatar Johannes Berg Committed by David S. Miller
Browse files

[PATCH] mac80211: fix iff_promiscs, iff_allmultis race 



When we update the counters iff_promiscs and iff_allmultis
in struct ieee80211_local we have no common lock held to
protect them. The problem is that the update to each counter
may not be atomic, so we could end up with iff_promiscs == -1
in unfortunate conditions. To fix it, use atomic_t values.
It doesn't matter whether the two counters are updated
together atomically or not, if there are two invocations
of set_multicast_list we will end up with multiple
configure_filter() invocations of which the latter will always
be correct.

Signed-off-by: default avatarJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
parent 50741ae0

net/mac80211/ieee80211.c

+6 −6
Original line number Diff line number Diff line
@@ -59,10 +59,10 @@ static void ieee80211_configure_filter(struct ieee80211_local *local) 
	unsigned int changed_flags;

	unsigned int new_flags = 0;



	if (local->iff_promiscs)

	if (atomic_read(&local->iff_promiscs))

		new_flags |= FIF_PROMISC_IN_BSS;



	if (local->iff_allmultis)

	if (atomic_read(&local->iff_allmultis))

		new_flags |= FIF_ALLMULTI;



	if (local->monitors)
@@ -521,17 +521,17 @@ static void ieee80211_set_multicast_list(struct net_device *dev) 


	if (allmulti != sdata_allmulti) {

		if (dev->flags & IFF_ALLMULTI)

			local->iff_allmultis++;

			atomic_inc(&local->iff_allmultis);

		else

			local->iff_allmultis--;

			atomic_dec(&local->iff_allmultis);

		sdata->flags ^= IEEE80211_SDATA_ALLMULTI;

	}



	if (promisc != sdata_promisc) {

		if (dev->flags & IFF_PROMISC)

			local->iff_promiscs++;

			atomic_inc(&local->iff_promiscs);

		else

			local->iff_promiscs--;

			atomic_dec(&local->iff_promiscs);

		sdata->flags ^= IEEE80211_SDATA_PROMISC;

	}

net/mac80211/ieee80211_i.h

+2 −3
Original line number Diff line number Diff line
@@ -444,9 +444,8 @@ struct ieee80211_local { 
	struct ieee80211_tx_stored_packet pending_packet[NUM_TX_DATA_QUEUES];

	struct tasklet_struct tx_pending_tasklet;



	int mc_count;	/* total count of multicast entries in all interfaces */

	int iff_allmultis, iff_promiscs;

	/* number of interfaces with corresponding IFF_ flags */

	atomic_t iff_allmultis, iff_promiscs;



	struct rate_control_ref *rate_ctrl;

net/mac80211/rx.c

+2 −1
Original line number Diff line number Diff line
@@ -1531,7 +1531,8 @@ void __ieee80211_rx(struct ieee80211_hw *hw, struct sk_buff *skb, 
	skb = rx.skb;



	if (sta && !(sta->flags & (WLAN_STA_WDS | WLAN_STA_ASSOC_AP)) &&

	    !local->iff_promiscs && !is_multicast_ether_addr(hdr->addr1)) {

	    !atomic_read(&local->iff_promiscs) &&

	    !is_multicast_ether_addr(hdr->addr1)) {

		rx.flags |= IEEE80211_TXRXD_RXRA_MATCH;

		ieee80211_invoke_rx_handlers(local, local->rx_handlers, &rx,

					     rx.sta);

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