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 <>
Signed-off-by: default avatarJohn W. Linville <>
parent 50741ae0
......@@ -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)
sdata->flags ^= IEEE80211_SDATA_ALLMULTI;
if (promisc != sdata_promisc) {
if (dev->flags & IFF_PROMISC)
sdata->flags ^= IEEE80211_SDATA_PROMISC;
......@@ -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 */
/* number of interfaces with corresponding IFF_ flags */
atomic_t iff_allmultis, iff_promiscs;
struct rate_control_ref *rate_ctrl;
......@@ -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,
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