[BRIDGE]: fix for RCU and deadlock on device removal

Change Bridge receive path to correctly handle RCU removal of device
from bridge.  Also fixes deadlock between carrier_check and del_nbp.
This replaces the previous deleted flag fix.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 10 deletions

diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index da687c8dc6f..70b7ef91723 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -79,9 +79,14 @@ static int port_cost(struct net_device *dev)
  */
 static void port_carrier_check(void *arg)
 {
-        struct net_bridge_port *p = arg;
+        struct net_device *dev = arg;
+        struct net_bridge_port *p;
 
         rtnl_lock();
+        p = dev->br_port;
+        if (!p)
+                goto done;
+
         if (netif_carrier_ok(p->dev)) {
                 u32 cost = port_cost(p->dev);
 
@@ -97,6 +102,7 @@ static void port_carrier_check(void *arg)
                         br_stp_disable_port(p);
                 spin_unlock_bh(&p->br->lock);
         }
+done:
         rtnl_unlock();
 }
 
@@ -104,7 +110,6 @@ static void destroy_nbp(struct net_bridge_port *p)
 {
         struct net_device *dev = p->dev;
 
-        dev->br_port = NULL;
         p->br = NULL;
         p->dev = NULL;
         dev_put(dev);
@@ -133,24 +138,20 @@ static void del_nbp(struct net_bridge_port *p)
         struct net_bridge *br = p->br;
         struct net_device *dev = p->dev;
 
-        /* Race between RTNL notify and RCU callback */
-        if (p->deleted)
-                return;
-
         dev_set_promiscuity(dev, -1);
 
         cancel_delayed_work(&p->carrier_check);
-        flush_scheduled_work();
 
         spin_lock_bh(&br->lock);
         br_stp_disable_port(p);
-        p->deleted = 1;
         spin_unlock_bh(&br->lock);
 
         br_fdb_delete_by_port(br, p);
 
         list_del_rcu(&p->list);
 
+        rcu_assign_pointer(dev->br_port, NULL);
+
         call_rcu(&p->rcu, destroy_nbp_rcu);
 }
 
@@ -254,11 +255,10 @@ static struct net_bridge_port *new_nbp(struct net_bridge *br,
         p->dev = dev;
         p->path_cost = port_cost(dev);
         p->priority = 0x8000 >> BR_PORT_BITS;
-        dev->br_port = p;
         p->port_no = index;
         br_init_port(p);
         p->state = BR_STATE_DISABLED;
-        INIT_WORK(&p->carrier_check, port_carrier_check, p);
+        INIT_WORK(&p->carrier_check, port_carrier_check, dev);
         kobject_init(&p->kobj);
 
         return p;
@@ -397,6 +397,7 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
         else if ((err = br_sysfs_addif(p)))
                 del_nbp(p);
         else {
+                rcu_assign_pointer(dev->br_port, p);
                 dev_set_promiscuity(dev, 1);
 
                 list_add_rcu(&p->list, &br->port_list);