bonding: eliminate bond_close race conditions

This patch resolves two sets of race conditions.

	Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com> reported the
first, as follows:

The bond_close() calls cancel_delayed_work() to cancel delayed works.
It, however, cannot cancel works that were already queued in workqueue.
The bond_open() initializes work->data, and proccess_one_work() refers
get_work_cwq(work)->wq->flags. The get_work_cwq() returns NULL when
work->data has been initialized. Thus, a panic occurs.

	He included a patch that converted the cancel_delayed_work calls
in bond_close to flush_delayed_work_sync, which eliminated the above
problem.

	His patch is incorporated, at least in principle, into this
patch.  In this patch, we use cancel_delayed_work_sync in place of
flush_delayed_work_sync, and also convert bond_uninit in addition to
bond_close.

	This conversion to _sync, however, opens new races between
bond_close and three periodically executing workqueue functions:
bond_mii_monitor, bond_alb_monitor and bond_activebackup_arp_mon.

	The race occurs because bond_close and bond_uninit are always
called with RTNL held, and these workqueue functions may acquire RTNL to
perform failover-related activities.  If bond_close or bond_uninit is
waiting in cancel_delayed_work_sync, deadlock occurs.

	These deadlocks are resolved by having the workqueue functions
acquire RTNL conditionally.  If the rtnl_trylock() fails, the functions
reschedule and return immediately.  For the cases that are attempting to
perform link failover, a delay of 1 is used; for the other cases, the
normal interval is used (as those activities are not as time critical).

	Additionally, the bond_mii_monitor function now stores the delay
in a variable (mimicing the structure of activebackup_arp_mon).

	Lastly, all of the above renders the kill_timers sentinel moot,
and therefore it has been removed.

Tested-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index b33c099d65a43b518e1c0d6547d680d5bb6fe565..0ae0d7c54ccf647e91792edfa14dc32d900ec877 100644 (file)
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -2110,9 +2110,6 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
 
        read_lock(&bond->lock);
 
-       if (bond->kill_timers)
-               goto out;
-
        //check if there are any slaves
        if (bond->slave_cnt == 0)
                goto re_arm;
@@ -2161,9 +2158,8 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
        }
 
 re_arm:
-       if (!bond->kill_timers)
-               queue_delayed_work(bond->wq, &bond->ad_work, ad_delta_in_ticks);
-out:
+       queue_delayed_work(bond->wq, &bond->ad_work, ad_delta_in_ticks);
+
        read_unlock(&bond->lock);
 }
 

diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index d4fbd2e62616cfc780a993c8ba4dc51a639f79bb..106b88a04738fb25fa5bd850537653beaa5b4aa5 100644 (file)
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -1343,10 +1343,6 @@ void bond_alb_monitor(struct work_struct *work)
 
        read_lock(&bond->lock);
 
-       if (bond->kill_timers) {
-               goto out;
-       }
-
        if (bond->slave_cnt == 0) {
                bond_info->tx_rebalance_counter = 0;
                bond_info->lp_counter = 0;
@@ -1401,10 +1397,13 @@ void bond_alb_monitor(struct work_struct *work)
 
                        /*
                         * dev_set_promiscuity requires rtnl and
-                        * nothing else.
+                        * nothing else.  Avoid race with bond_close.
                         */
                        read_unlock(&bond->lock);
-                       rtnl_lock();
+                       if (!rtnl_trylock()) {
+                               read_lock(&bond->lock);
+                               goto re_arm;
+                       }
 
                        bond_info->rlb_promisc_timeout_counter = 0;
 
@@ -1440,9 +1439,8 @@ void bond_alb_monitor(struct work_struct *work)
        }
 
 re_arm:
-       if (!bond->kill_timers)
-               queue_delayed_work(bond->wq, &bond->alb_work, alb_delta_in_ticks);
-out:
+       queue_delayed_work(bond->wq, &bond->alb_work, alb_delta_in_ticks);
+
        read_unlock(&bond->lock);
 }
 

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index c5944f1a4f9d52da7820337d8fb2324727724048..c34cc1e7c6f6d9b413b899cc66a6356066155d32 100644 (file)
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -773,9 +773,6 @@ static void bond_resend_igmp_join_requests(struct bonding *bond)
 
        read_lock(&bond->lock);
 
-       if (bond->kill_timers)
-               goto out;
-
        /* rejoin all groups on bond device */
        __bond_resend_igmp_join_requests(bond->dev);
 
@@ -789,9 +786,9 @@ static void bond_resend_igmp_join_requests(struct bonding *bond)
                        __bond_resend_igmp_join_requests(vlan_dev);
        }
 
-       if ((--bond->igmp_retrans > 0) && !bond->kill_timers)
+       if (--bond->igmp_retrans > 0)
                queue_delayed_work(bond->wq, &bond->mcast_work, HZ/5);
-out:
+
        read_unlock(&bond->lock);
 }
 
@@ -2517,10 +2514,11 @@ void bond_mii_monitor(struct work_struct *work)
        struct bonding *bond = container_of(work, struct bonding,
                                            mii_work.work);
        bool should_notify_peers = false;
+       unsigned long delay;
 
        read_lock(&bond->lock);
-       if (bond->kill_timers)
-               goto out;
+
+       delay = msecs_to_jiffies(bond->params.miimon);
 
        if (bond->slave_cnt == 0)
                goto re_arm;
@@ -2529,7 +2527,15 @@ void bond_mii_monitor(struct work_struct *work)
 
        if (bond_miimon_inspect(bond)) {
                read_unlock(&bond->lock);
-               rtnl_lock();
+
+               /* Race avoidance with bond_close cancel of workqueue */
+               if (!rtnl_trylock()) {
+                       read_lock(&bond->lock);
+                       delay = 1;
+                       should_notify_peers = false;
+                       goto re_arm;
+               }
+
                read_lock(&bond->lock);
 
                bond_miimon_commit(bond);
@@ -2540,14 +2546,18 @@ void bond_mii_monitor(struct work_struct *work)
        }
 
 re_arm:
-       if (bond->params.miimon && !bond->kill_timers)
-               queue_delayed_work(bond->wq, &bond->mii_work,
-                                  msecs_to_jiffies(bond->params.miimon));
-out:
+       if (bond->params.miimon)
+               queue_delayed_work(bond->wq, &bond->mii_work, delay);
+
        read_unlock(&bond->lock);
 
        if (should_notify_peers) {
-               rtnl_lock();
+               if (!rtnl_trylock()) {
+                       read_lock(&bond->lock);
+                       bond->send_peer_notif++;
+                       read_unlock(&bond->lock);
+                       return;
+               }
                netdev_bonding_change(bond->dev, NETDEV_NOTIFY_PEERS);
                rtnl_unlock();
        }
@@ -2789,9 +2799,6 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
 
        delta_in_ticks = msecs_to_jiffies(bond->params.arp_interval);
 
-       if (bond->kill_timers)
-               goto out;
-
        if (bond->slave_cnt == 0)
                goto re_arm;
 
@@ -2888,9 +2895,9 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
        }
 
 re_arm:
-       if (bond->params.arp_interval && !bond->kill_timers)
+       if (bond->params.arp_interval)
                queue_delayed_work(bond->wq, &bond->arp_work, delta_in_ticks);
-out:
+
        read_unlock(&bond->lock);
 }
 
@@ -3131,9 +3138,6 @@ void bond_activebackup_arp_mon(struct work_struct *work)
 
        read_lock(&bond->lock);
 
-       if (bond->kill_timers)
-               goto out;
-
        delta_in_ticks = msecs_to_jiffies(bond->params.arp_interval);
 
        if (bond->slave_cnt == 0)
@@ -3143,7 +3147,15 @@ void bond_activebackup_arp_mon(struct work_struct *work)
 
        if (bond_ab_arp_inspect(bond, delta_in_ticks)) {
                read_unlock(&bond->lock);
-               rtnl_lock();
+
+               /* Race avoidance with bond_close flush of workqueue */
+               if (!rtnl_trylock()) {
+                       read_lock(&bond->lock);
+                       delta_in_ticks = 1;
+                       should_notify_peers = false;
+                       goto re_arm;
+               }
+
                read_lock(&bond->lock);
 
                bond_ab_arp_commit(bond, delta_in_ticks);
@@ -3156,13 +3168,18 @@ void bond_activebackup_arp_mon(struct work_struct *work)
        bond_ab_arp_probe(bond);
 
 re_arm:
-       if (bond->params.arp_interval && !bond->kill_timers)
+       if (bond->params.arp_interval)
                queue_delayed_work(bond->wq, &bond->arp_work, delta_in_ticks);
-out:
+
        read_unlock(&bond->lock);
 
        if (should_notify_peers) {
-               rtnl_lock();
+               if (!rtnl_trylock()) {
+                       read_lock(&bond->lock);
+                       bond->send_peer_notif++;
+                       read_unlock(&bond->lock);
+                       return;
+               }
                netdev_bonding_change(bond->dev, NETDEV_NOTIFY_PEERS);
                rtnl_unlock();
        }
@@ -3424,8 +3441,6 @@ static int bond_open(struct net_device *bond_dev)
        struct slave *slave;
        int i;
 
-       bond->kill_timers = 0;
-
        /* reset slave->backup and slave->inactive */
        read_lock(&bond->lock);
        if (bond->slave_cnt > 0) {
@@ -3494,33 +3509,30 @@ static int bond_close(struct net_device *bond_dev)
 
        bond->send_peer_notif = 0;
 
-       /* signal timers not to re-arm */
-       bond->kill_timers = 1;
-
        write_unlock_bh(&bond->lock);
 
        if (bond->params.miimon) {  /* link check interval, in milliseconds. */
-               cancel_delayed_work(&bond->mii_work);
+               cancel_delayed_work_sync(&bond->mii_work);
        }
 
        if (bond->params.arp_interval) {  /* arp interval, in milliseconds. */
-               cancel_delayed_work(&bond->arp_work);
+               cancel_delayed_work_sync(&bond->arp_work);
        }
 
        switch (bond->params.mode) {
        case BOND_MODE_8023AD:
-               cancel_delayed_work(&bond->ad_work);
+               cancel_delayed_work_sync(&bond->ad_work);
                break;
        case BOND_MODE_TLB:
        case BOND_MODE_ALB:
-               cancel_delayed_work(&bond->alb_work);
+               cancel_delayed_work_sync(&bond->alb_work);
                break;
        default:
                break;
        }
 
        if (delayed_work_pending(&bond->mcast_work))
-               cancel_delayed_work(&bond->mcast_work);
+               cancel_delayed_work_sync(&bond->mcast_work);
 
        if (bond_is_lb(bond)) {
                /* Must be called only after all
@@ -4367,26 +4379,22 @@ static void bond_setup(struct net_device *bond_dev)
 
 static void bond_work_cancel_all(struct bonding *bond)
 {
-       write_lock_bh(&bond->lock);
-       bond->kill_timers = 1;
-       write_unlock_bh(&bond->lock);
-
        if (bond->params.miimon && delayed_work_pending(&bond->mii_work))
-               cancel_delayed_work(&bond->mii_work);
+               cancel_delayed_work_sync(&bond->mii_work);
 
        if (bond->params.arp_interval && delayed_work_pending(&bond->arp_work))
-               cancel_delayed_work(&bond->arp_work);
+               cancel_delayed_work_sync(&bond->arp_work);
 
        if (bond->params.mode == BOND_MODE_ALB &&
            delayed_work_pending(&bond->alb_work))
-               cancel_delayed_work(&bond->alb_work);
+               cancel_delayed_work_sync(&bond->alb_work);
 
        if (bond->params.mode == BOND_MODE_8023AD &&
            delayed_work_pending(&bond->ad_work))
-               cancel_delayed_work(&bond->ad_work);
+               cancel_delayed_work_sync(&bond->ad_work);
 
        if (delayed_work_pending(&bond->mcast_work))
-               cancel_delayed_work(&bond->mcast_work);
+               cancel_delayed_work_sync(&bond->mcast_work);
 }
 
 /*

diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
index 82fec5fc75d7fd84fc861516cd356ae793feb41c..1aecc37e5b4dcd041cefecc1fb3e7813ab39d8b0 100644 (file)
--- a/drivers/net/bonding/bonding.h
+++ b/drivers/net/bonding/bonding.h
@@ -222,7 +222,6 @@ struct bonding {
                               struct slave *);
        rwlock_t lock;
        rwlock_t curr_slave_lock;
-       s8       kill_timers;
        u8       send_peer_notif;
        s8       setup_by_slave;
        s8       igmp_retrans;