batman-adv: protect softif_neigh by rcu

Add get/set wrapper functions for softif_neigh and
use rcu functions to manipulate the pointers.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>

2 files changed, 88 insertions, 28 deletions

diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 9ed26140a269..ad6da4c7ddb5 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -90,10 +90,51 @@ static void softif_neigh_free_ref(struct softif_neigh *softif_neigh)
                 call_rcu(&softif_neigh->rcu, softif_neigh_free_rcu);
 }
 
+static struct softif_neigh *softif_neigh_get_selected(struct bat_priv *bat_priv)
+{
+        struct softif_neigh *neigh;
+
+        rcu_read_lock();
+        neigh = rcu_dereference(bat_priv->softif_neigh);
+
+        if (neigh && !atomic_inc_not_zero(&neigh->refcount))
+                neigh = NULL;
+
+        rcu_read_unlock();
+        return neigh;
+}
+
+static void softif_neigh_select(struct bat_priv *bat_priv,
+                                struct softif_neigh *new_neigh)
+{
+        struct softif_neigh *curr_neigh;
+
+        spin_lock_bh(&bat_priv->softif_neigh_lock);
+
+        if (new_neigh && !atomic_inc_not_zero(&new_neigh->refcount))
+                new_neigh = NULL;
+
+        curr_neigh = bat_priv->softif_neigh;
+        rcu_assign_pointer(bat_priv->softif_neigh, new_neigh);
+
+        if (curr_neigh)
+                softif_neigh_free_ref(curr_neigh);
+
+        spin_unlock_bh(&bat_priv->softif_neigh_lock);
+}
+
+static void softif_neigh_deselect(struct bat_priv *bat_priv)
+{
+        softif_neigh_select(bat_priv, NULL);
+}
+
 void softif_neigh_purge(struct bat_priv *bat_priv)
 {
-        struct softif_neigh *softif_neigh, *softif_neigh_tmp;
+        struct softif_neigh *softif_neigh, *curr_softif_neigh;
         struct hlist_node *node, *node_tmp;
+        char do_deselect = 0;
+
+        curr_softif_neigh = softif_neigh_get_selected(bat_priv);
 
         spin_lock_bh(&bat_priv->softif_neigh_lock);
 
@@ -105,22 +146,26 @@ void softif_neigh_purge(struct bat_priv *bat_priv)
                     (atomic_read(&bat_priv->mesh_state) == MESH_ACTIVE))
                         continue;
 
-                hlist_del_rcu(&softif_neigh->list);
-
-                if (bat_priv->softif_neigh == softif_neigh) {
+                if (curr_softif_neigh == softif_neigh) {
                         bat_dbg(DBG_ROUTES, bat_priv,
                                  "Current mesh exit point '%pM' vanished "
                                  "(vid: %d).\n",
                                  softif_neigh->addr, softif_neigh->vid);
-                        softif_neigh_tmp = bat_priv->softif_neigh;
-                        bat_priv->softif_neigh = NULL;
-                        softif_neigh_free_ref(softif_neigh_tmp);
+                        do_deselect = 1;
                 }
 
+                hlist_del_rcu(&softif_neigh->list);
                 softif_neigh_free_ref(softif_neigh);
         }
 
         spin_unlock_bh(&bat_priv->softif_neigh_lock);
+
+        /* soft_neigh_deselect() needs to acquire the softif_neigh_lock */
+        if (do_deselect)
+                softif_neigh_deselect(bat_priv);
+
+        if (curr_softif_neigh)
+                softif_neigh_free_ref(curr_softif_neigh);
 }
 
 static struct softif_neigh *softif_neigh_get(struct bat_priv *bat_priv,
@@ -171,6 +216,7 @@ int softif_neigh_seq_print_text(struct seq_file *seq, void *offset)
         struct bat_priv *bat_priv = netdev_priv(net_dev);
         struct softif_neigh *softif_neigh;
         struct hlist_node *node;
+        struct softif_neigh *curr_softif_neigh;
 
         if (!bat_priv->primary_if) {
                 return seq_printf(seq, "BATMAN mesh %s disabled - "
@@ -180,14 +226,17 @@ int softif_neigh_seq_print_text(struct seq_file *seq, void *offset)
 
         seq_printf(seq, "Softif neighbor list (%s)\n", net_dev->name);
 
+        curr_softif_neigh = softif_neigh_get_selected(bat_priv);
         rcu_read_lock();
         hlist_for_each_entry_rcu(softif_neigh, node,
                                  &bat_priv->softif_neigh_list, list)
                 seq_printf(seq, "%s %pM (vid: %d)\n",
-                                bat_priv->softif_neigh == softif_neigh
+                                curr_softif_neigh == softif_neigh
                                 ? "=>" : "  ", softif_neigh->addr,
                                 softif_neigh->vid);
         rcu_read_unlock();
+        if (curr_softif_neigh)
+                softif_neigh_free_ref(curr_softif_neigh);
 
         return 0;
 }
@@ -198,7 +247,8 @@ static void softif_batman_recv(struct sk_buff *skb, struct net_device *dev,
         struct bat_priv *bat_priv = netdev_priv(dev);
         struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
         struct batman_packet *batman_packet;
-        struct softif_neigh *softif_neigh, *softif_neigh_tmp;
+        struct softif_neigh *softif_neigh;
+        struct softif_neigh *curr_softif_neigh = NULL;
 
         if (ntohs(ethhdr->h_proto) == ETH_P_8021Q)
                 batman_packet = (struct batman_packet *)
@@ -223,7 +273,8 @@ static void softif_batman_recv(struct sk_buff *skb, struct net_device *dev,
         if (!softif_neigh)
                 goto err;
 
-        if (bat_priv->softif_neigh == softif_neigh)
+        curr_softif_neigh = softif_neigh_get_selected(bat_priv);
+        if (curr_softif_neigh == softif_neigh)
                 goto out;
 
         /* we got a neighbor but its mac is 'bigger' than ours  */
@@ -232,38 +283,39 @@ static void softif_batman_recv(struct sk_buff *skb, struct net_device *dev,
                 goto out;
 
         /* switch to new 'smallest neighbor' */
-        if ((bat_priv->softif_neigh) &&
-            (memcmp(softif_neigh->addr, bat_priv->softif_neigh->addr,
+        if ((curr_softif_neigh) &&
+            (memcmp(softif_neigh->addr, curr_softif_neigh->addr,
                                                         ETH_ALEN) < 0)) {
                 bat_dbg(DBG_ROUTES, bat_priv,
                         "Changing mesh exit point from %pM (vid: %d) "
                         "to %pM (vid: %d).\n",
-                         bat_priv->softif_neigh->addr,
-                         bat_priv->softif_neigh->vid,
+                         curr_softif_neigh->addr,
+                         curr_softif_neigh->vid,
                          softif_neigh->addr, softif_neigh->vid);
-                softif_neigh_tmp = bat_priv->softif_neigh;
-                bat_priv->softif_neigh = softif_neigh;
-                softif_neigh_free_ref(softif_neigh_tmp);
-                /* we need to hold the additional reference */
-                goto err;
+
+                softif_neigh_select(bat_priv, softif_neigh);
+                goto out;
         }
 
         /* close own batX device and use softif_neigh as exit node */
-        if ((!bat_priv->softif_neigh) &&
+        if ((!curr_softif_neigh) &&
             (memcmp(softif_neigh->addr,
                     bat_priv->primary_if->net_dev->dev_addr, ETH_ALEN) < 0)) {
                 bat_dbg(DBG_ROUTES, bat_priv,
                         "Setting mesh exit point to %pM (vid: %d).\n",
                         softif_neigh->addr, softif_neigh->vid);
-                bat_priv->softif_neigh = softif_neigh;
-                /* we need to hold the additional reference */
-                goto err;
+
+                softif_neigh_select(bat_priv, softif_neigh);
+                goto out;
         }
 
 out:
         softif_neigh_free_ref(softif_neigh);
 err:
         kfree_skb(skb);
+        if (curr_softif_neigh)
+                softif_neigh_free_ref(curr_softif_neigh);
+
         return;
 }
 
@@ -321,6 +373,7 @@ int interface_tx(struct sk_buff *skb, struct net_device *soft_iface)
         struct bat_priv *bat_priv = netdev_priv(soft_iface);
         struct bcast_packet *bcast_packet;
         struct vlan_ethhdr *vhdr;
+        struct softif_neigh *curr_softif_neigh = NULL;
         int data_len = skb->len, ret;
         short vid = -1;
         bool do_bcast = false;
@@ -348,7 +401,8 @@ int interface_tx(struct sk_buff *skb, struct net_device *soft_iface)
          * if we have a another chosen mesh exit node in range
          * it will transport the packets to the mesh
          */
-        if ((bat_priv->softif_neigh) && (bat_priv->softif_neigh->vid == vid))
+        curr_softif_neigh = softif_neigh_get_selected(bat_priv);
+        if ((curr_softif_neigh) && (curr_softif_neigh->vid == vid))
                 goto dropped;
 
         /* TODO: check this for locks */
@@ -410,6 +464,8 @@ dropped:
 dropped_freed:
         bat_priv->stats.tx_dropped++;
 end:
+        if (curr_softif_neigh)
+                softif_neigh_free_ref(curr_softif_neigh);
         return NETDEV_TX_OK;
 }
 
@@ -421,6 +477,7 @@ void interface_rx(struct net_device *soft_iface,
         struct unicast_packet *unicast_packet;
         struct ethhdr *ethhdr;
         struct vlan_ethhdr *vhdr;
+        struct softif_neigh *curr_softif_neigh = NULL;
         short vid = -1;
         int ret;
 
@@ -450,7 +507,8 @@ void interface_rx(struct net_device *soft_iface,
          * if we have a another chosen mesh exit node in range
          * it will transport the packets to the non-mesh network
          */
-        if ((bat_priv->softif_neigh) && (bat_priv->softif_neigh->vid == vid)) {
+        curr_softif_neigh = softif_neigh_get_selected(bat_priv);
+        if (curr_softif_neigh && (curr_softif_neigh->vid == vid)) {
                 skb_push(skb, hdr_size);
                 unicast_packet = (struct unicast_packet *)skb->data;
 
@@ -461,7 +519,7 @@ void interface_rx(struct net_device *soft_iface,
                 skb_reset_mac_header(skb);
 
                 memcpy(unicast_packet->dest,
-                       bat_priv->softif_neigh->addr, ETH_ALEN);
+                       curr_softif_neigh->addr, ETH_ALEN);
                 ret = route_unicast_packet(skb, recv_if);
                 if (ret == NET_RX_DROP)
                         goto dropped;
@@ -486,11 +544,13 @@ void interface_rx(struct net_device *soft_iface,
         soft_iface->last_rx = jiffies;
 
         netif_rx(skb);
-        return;
+        goto out;
 
 dropped:
         kfree_skb(skb);
 out:
+        if (curr_softif_neigh)
+                softif_neigh_free_ref(curr_softif_neigh);
         return;
 }
 
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 091476df4f0e..75123b1ae0de 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -147,7 +147,7 @@ struct bat_priv {
         atomic_t batman_queue_left;
         char num_ifaces;
         struct hlist_head softif_neigh_list;
-        struct softif_neigh *softif_neigh;
+        struct softif_neigh __rcu *softif_neigh;
         struct debug_log *debug_log;
         struct hard_iface *primary_if;
         struct kobject *mesh_obj;