Merge branch 'bonding'

Veaceslav Falico says:

====================
bonding: fix locking in bond_ab_arp_prob

After the latest patches, on every call of bond_ab_arp_probe() without an
active slave I see the following warning:

[    7.912314] RTNL: assertion failed at net/core/dev.c (4494)
...
[    7.922495]  [<ffffffff817acc6f>] dump_stack+0x51/0x72
[    7.923714]  [<ffffffff8168795e>] netdev_master_upper_dev_get+0x6e/0x70
[    7.924940]  [<ffffffff816a2a66>] rtnl_link_fill+0x116/0x260
[    7.926143]  [<ffffffff817acc6f>] ? dump_stack+0x51/0x72
[    7.927333]  [<ffffffff816a350c>] rtnl_fill_ifinfo+0x95c/0xb90
[    7.928529]  [<ffffffff8167af2b>] ? __kmalloc_reserve+0x3b/0xa0
[    7.929681]  [<ffffffff8167bfcf>] ? __alloc_skb+0x9f/0x1e0
[    7.930827]  [<ffffffff816a3b64>] rtmsg_ifinfo+0x84/0x100
[    7.931960]  [<ffffffffa00bca07>] bond_ab_arp_probe+0x1a7/0x370 [bonding]
[    7.933133]  [<ffffffffa00bcd78>] bond_activebackup_arp_mon+0x1a8/0x2f0 [bonding]
...

It happens because in bond_ab_arp_probe() we change the flags of a slave
without holding the RTNL lock.

To fix this - remove the useless curr_active_lock, RCUify it and lock RTNL
while changing the slave's flags. Also, remove bond_ab_arp_probe() from
under any locks in bond_ab_arp_mon().
====================

Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index a7db819bca9278356598152060c4684bd6f615c7..dd75615d85f2d0dfb18911cd1ac0ab59ebad5cbb 100644 (file)
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2599,45 +2599,51 @@ do_failover:
 
 /*
  * Send ARP probes for active-backup mode ARP monitor.
- *
- * Called with rcu_read_lock hold.
  */
-static void bond_ab_arp_probe(struct bonding *bond)
+static bool bond_ab_arp_probe(struct bonding *bond)
 {
        struct slave *slave, *before = NULL, *new_slave = NULL,
-                    *curr_arp_slave = rcu_dereference(bond->current_arp_slave);
+                    *curr_arp_slave, *curr_active_slave;
        struct list_head *iter;
        bool found = false;
 
-       read_lock(&bond->curr_slave_lock);
+       rcu_read_lock();
+       curr_arp_slave = rcu_dereference(bond->current_arp_slave);
+       curr_active_slave = rcu_dereference(bond->curr_active_slave);
 
-       if (curr_arp_slave && bond->curr_active_slave)
+       if (curr_arp_slave && curr_active_slave)
                pr_info("PROBE: c_arp %s && cas %s BAD\n",
                        curr_arp_slave->dev->name,
-                       bond->curr_active_slave->dev->name);
+                       curr_active_slave->dev->name);
 
-       if (bond->curr_active_slave) {
-               bond_arp_send_all(bond, bond->curr_active_slave);
-               read_unlock(&bond->curr_slave_lock);
-               return;
+       if (curr_active_slave) {
+               bond_arp_send_all(bond, curr_active_slave);
+               rcu_read_unlock();
+               return true;
        }
-
-       read_unlock(&bond->curr_slave_lock);
+       rcu_read_unlock();
 
        /* if we don't have a curr_active_slave, search for the next available
         * backup slave from the current_arp_slave and make it the candidate
         * for becoming the curr_active_slave
         */
 
+       if (!rtnl_trylock())
+               return false;
+       /* curr_arp_slave might have gone away */
+       curr_arp_slave = ACCESS_ONCE(bond->current_arp_slave);
+
        if (!curr_arp_slave) {
-               curr_arp_slave = bond_first_slave_rcu(bond);
-               if (!curr_arp_slave)
-                       return;
+               curr_arp_slave = bond_first_slave(bond);
+               if (!curr_arp_slave) {
+                       rtnl_unlock();
+                       return true;
+               }
        }
 
        bond_set_slave_inactive_flags(curr_arp_slave);
 
-       bond_for_each_slave_rcu(bond, slave, iter) {
+       bond_for_each_slave(bond, slave, iter) {
                if (!found && !before && IS_UP(slave->dev))
                        before = slave;
 
@@ -2667,21 +2673,26 @@ static void bond_ab_arp_probe(struct bonding *bond)
        if (!new_slave && before)
                new_slave = before;
 
-       if (!new_slave)
-               return;
+       if (!new_slave) {
+               rtnl_unlock();
+               return true;
+       }
 
        new_slave->link = BOND_LINK_BACK;
        bond_set_slave_active_flags(new_slave);
        bond_arp_send_all(bond, new_slave);
        new_slave->jiffies = jiffies;
        rcu_assign_pointer(bond->current_arp_slave, new_slave);
+       rtnl_unlock();
+
+       return true;
 }
 
 static void bond_activebackup_arp_mon(struct work_struct *work)
 {
        struct bonding *bond = container_of(work, struct bonding,
                                            arp_work.work);
-       bool should_notify_peers = false;
+       bool should_notify_peers = false, should_commit = false;
        int delta_in_ticks;
 
        delta_in_ticks = msecs_to_jiffies(bond->params.arp_interval);
@@ -2690,12 +2701,11 @@ static void bond_activebackup_arp_mon(struct work_struct *work)
                goto re_arm;
 
        rcu_read_lock();
-
        should_notify_peers = bond_should_notify_peers(bond);
+       should_commit = bond_ab_arp_inspect(bond);
+       rcu_read_unlock();
 
-       if (bond_ab_arp_inspect(bond)) {
-               rcu_read_unlock();
-
+       if (should_commit) {
                /* Race avoidance with bond_close flush of workqueue */
                if (!rtnl_trylock()) {
                        delta_in_ticks = 1;
@@ -2704,13 +2714,14 @@ static void bond_activebackup_arp_mon(struct work_struct *work)
                }
 
                bond_ab_arp_commit(bond);
-
                rtnl_unlock();
-               rcu_read_lock();
        }
 
-       bond_ab_arp_probe(bond);
-       rcu_read_unlock();
+       if (!bond_ab_arp_probe(bond)) {
+               /* rtnl locking failed, re-arm */
+               delta_in_ticks = 1;
+               should_notify_peers = false;
+       }
 
 re_arm:
        if (bond->params.arp_interval)