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Commit b0d11b42 authored by Jiri Pirko's avatar Jiri Pirko Committed by David S. Miller
Browse files

team: avoid possible underflow of count_pending value for notify_peers and mcast_rejoin 



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: fc423ff0 ("team: add peer notification")
Fixes: 492b200e  ("team: add support for sending multicast rejoins")
Signed-off-by: default avatarJiri Pirko <jiri@resnulli.us>
Signed-off-by: default avatarJiri Benc <jbenc@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1ba39804

drivers/net/team/team.c

+14 −2
Original line number Diff line number Diff line
@@ -629,6 +629,7 @@ 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);
@@ -636,9 +637,14 @@ static void team_notify_peers_work(struct work_struct *work) 
		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));

}
@@ -669,6 +675,7 @@ 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);
@@ -676,9 +683,14 @@ static void team_mcast_rejoin_work(struct work_struct *work) 
		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));

}