[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, 3 deletions

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 32d19bbf522c..38e0a467fa8e 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -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;