team: avoid possible underflow of count_pending value for notify_peer…

…s and mcast_rejoin [ Upstream commit b0d11b4 ] This patch is fixing a race condition that may cause setting count_pending to -1, which results in unwanted big bulk of arp messages (in case of "notify peers"). Consider following scenario: count_pending == 2 CPU0 CPU1 team_notify_peers_work atomic_dec_and_test (dec count_pending to 1) schedule_delayed_work team_notify_peers atomic_add (adding 1 to count_pending) team_notify_peers_work atomic_dec_and_test (dec count_pending to 1) schedule_delayed_work team_notify_peers_work atomic_dec_and_test (dec count_pending to 0) schedule_delayed_work team_notify_peers_work atomic_dec_and_test (dec count_pending to -1) Fix this race by using atomic_dec_if_positive - that will prevent count_pending running under 0. Fixes: fc423ff ("team: add peer notification") Fixes: 492b200 ("team: add support for sending multicast rejoins") Signed-off-by: Jiri Pirko <[email protected]> Signed-off-by: Jiri Benc <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
fastly · Jan 27, 2015 · 58f2f9c · 58f2f9c
1 parent ff9df48
commit 58f2f9c
Showing 1 changed file with 14 additions and 2 deletions.
diff --git a/drivers/net/team/team.c b/drivers/net/team/team.c
@@ -629,16 +629,22 @@ static int team_change_mode(struct team *team, const char *kind)
 static void team_notify_peers_work(struct work_struct *work)
 {
 	struct team *team;
+	int val;
 
 	team = container_of(work, struct team, notify_peers.dw.work);
 
 	if (!rtnl_trylock()) {
 		schedule_delayed_work(&team->notify_peers.dw, 0);
 		return;
 	}
+	val = atomic_dec_if_positive(&team->notify_peers.count_pending);
+	if (val < 0) {
+		rtnl_unlock();
+		return;
+	}
 	call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, team->dev);
 	rtnl_unlock();
-	if (!atomic_dec_and_test(&team->notify_peers.count_pending))
+	if (val)
 		schedule_delayed_work(&team->notify_peers.dw,
 				      msecs_to_jiffies(team->notify_peers.interval));
 }
@@ -669,16 +675,22 @@ static void team_notify_peers_fini(struct team *team)
 static void team_mcast_rejoin_work(struct work_struct *work)
 {
 	struct team *team;
+	int val;
 
 	team = container_of(work, struct team, mcast_rejoin.dw.work);
 
 	if (!rtnl_trylock()) {
 		schedule_delayed_work(&team->mcast_rejoin.dw, 0);
 		return;
 	}
+	val = atomic_dec_if_positive(&team->mcast_rejoin.count_pending);
+	if (val < 0) {
+		rtnl_unlock();
+		return;
+	}
 	call_netdevice_notifiers(NETDEV_RESEND_IGMP, team->dev);
 	rtnl_unlock();
-	if (!atomic_dec_and_test(&team->mcast_rejoin.count_pending))
+	if (val)
 		schedule_delayed_work(&team->mcast_rejoin.dw,
 				      msecs_to_jiffies(team->mcast_rejoin.interval));
 }