[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: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 34adc5288fbc..03635fb3e9b6 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -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);