| From | Jiri Slaby <> | Subject | [PATCH 3.12 065/176] team: avoid possible underflow of count_pending value for notify_peers and mcast_rejoin | Date | Wed, 28 Jan 2015 15:28:15 +0100 |
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From: Jiri Pirko <jiri@resnulli.us>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
[ Upstream commit b0d11b42785b70e19bc6a3122eead3f7969a7589 ]
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: fc423ff00df3a1955441 ("team: add peer notification") Fixes: 492b200efdd20b8fcfd ("team: add support for sending multicast rejoins") Signed-off-by: Jiri Pirko <jiri@resnulli.us> Signed-off-by: Jiri Benc <jbenc@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Jiri Slaby <jslaby@suse.cz> --- drivers/net/team/team.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/drivers/net/team/team.c b/drivers/net/team/team.c index 75864dfaa1c2..258f65ba733f 100644 --- a/drivers/net/team/team.c +++ b/drivers/net/team/team.c @@ -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)); } -- 2.2.2
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