[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>

4 files changed, 41 insertions, 30 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);
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index e3a73cead6b..4eef8375531 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -45,18 +45,20 @@ static void br_pass_frame_up(struct net_bridge *br, struct sk_buff *skb)
 int br_handle_frame_finish(struct sk_buff *skb)
 {
         const unsigned char *dest = eth_hdr(skb)->h_dest;
-        struct net_bridge_port *p = skb->dev->br_port;
-        struct net_bridge *br = p->br;
+        struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
+        struct net_bridge *br;
         struct net_bridge_fdb_entry *dst;
         int passedup = 0;
 
+        if (!p || p->state == BR_STATE_DISABLED)
+                goto drop;
+
         /* insert into forwarding database after filtering to avoid spoofing */
-        br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
+        br = p->br;
+        br_fdb_update(br, p, eth_hdr(skb)->h_source);
 
-        if (p->state == BR_STATE_LEARNING) {
-                kfree_skb(skb);
-                goto out;
-        }
+        if (p->state == BR_STATE_LEARNING)
+                goto drop;
 
         if (br->dev->flags & IFF_PROMISC) {
                 struct sk_buff *skb2;
@@ -93,6 +95,9 @@ int br_handle_frame_finish(struct sk_buff *skb)
 
 out:
         return 0;
+drop:
+        kfree_skb(skb);
+        goto out;
 }
 
 /*
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index e330b17b6d8..c5bd631ffcd 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -68,7 +68,6 @@ struct net_bridge_port
         /* STP */
         u8                              priority;
         u8                              state;
-        u8                              deleted;
         u16                             port_no;
         unsigned char                   topology_change_ack;
         unsigned char                   config_pending;
diff --git a/net/bridge/br_stp_bpdu.c b/net/bridge/br_stp_bpdu.c
index d071f1c9ad0..296f6a487c5 100644
--- a/net/bridge/br_stp_bpdu.c
+++ b/net/bridge/br_stp_bpdu.c
@@ -133,29 +133,35 @@ void br_send_tcn_bpdu(struct net_bridge_port *p)
 
 static const unsigned char header[6] = {0x42, 0x42, 0x03, 0x00, 0x00, 0x00};
 
-/* NO locks */
+/* NO locks, but rcu_read_lock (preempt_disabled)  */
 int br_stp_handle_bpdu(struct sk_buff *skb)
 {
-        struct net_bridge_port *p = skb->dev->br_port;
-        struct net_bridge *br = p->br;
+        struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
+        struct net_bridge *br;
         unsigned char *buf;
 
+        if (!p)
+                goto err;
+
+        br = p->br;
+        spin_lock(&br->lock);
+
+        if (p->state == BR_STATE_DISABLED || !(br->dev->flags & IFF_UP))
+                goto out;
+
         /* insert into forwarding database after filtering to avoid spoofing */
-        br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
+        br_fdb_update(br, p, eth_hdr(skb)->h_source);
+
+        if (!br->stp_enabled)
+                goto out;
 
         /* need at least the 802 and STP headers */
         if (!pskb_may_pull(skb, sizeof(header)+1) ||
             memcmp(skb->data, header, sizeof(header)))
-                goto err;
+                goto out;
 
         buf = skb_pull(skb, sizeof(header));
 
-        spin_lock_bh(&br->lock);
-        if (p->state == BR_STATE_DISABLED 
-            || !(br->dev->flags & IFF_UP)
-            || !br->stp_enabled)
-                goto out;
-
         if (buf[0] == BPDU_TYPE_CONFIG) {
                 struct br_config_bpdu bpdu;
 
@@ -201,7 +207,7 @@ int br_stp_handle_bpdu(struct sk_buff *skb)
                 br_received_tcn_bpdu(p);
         }
  out:
-        spin_unlock_bh(&br->lock);
+        spin_unlock(&br->lock);
  err:
         kfree_skb(skb);
         return 0;