batman-adv: Make orig_node->router an rcu protected pointer

The rcu protected macros rcu_dereference() and rcu_assign_pointer()
for the orig_node->router need to be used, as well as spin/rcu locking.
Otherwise we might end up using a router pointer pointing to already
freed memory.

Therefore this commit introduces the safe getter method
orig_node_get_router().

Signed-off-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>

1 files changed, 45 insertions, 46 deletions

diff --git a/net/batman-adv/vis.c b/net/batman-adv/vis.c
index f90212f42082..d4cc4f5399f4 100644
--- a/net/batman-adv/vis.c
+++ b/net/batman-adv/vis.c
@@ -558,6 +558,7 @@ static int find_best_vis_server(struct bat_priv *bat_priv,
                                 struct vis_info *info)
 {
         struct hashtable_t *hash = bat_priv->orig_hash;
+        struct neigh_node *router;
         struct hlist_node *node;
         struct hlist_head *head;
         struct orig_node *orig_node;
@@ -571,13 +572,17 @@ static int find_best_vis_server(struct bat_priv *bat_priv,
 
                 rcu_read_lock();
                 hlist_for_each_entry_rcu(orig_node, node, head, hash_entry) {
-                        if ((orig_node) && (orig_node->router) &&
-                            (orig_node->flags & VIS_SERVER) &&
-                            (orig_node->router->tq_avg > best_tq)) {
-                                best_tq = orig_node->router->tq_avg;
+                        router = orig_node_get_router(orig_node);
+                        if (!router)
+                                continue;
+
+                        if ((orig_node->flags & VIS_SERVER) &&
+                            (router->tq_avg > best_tq)) {
+                                best_tq = router->tq_avg;
                                 memcpy(packet->target_orig, orig_node->orig,
                                        ETH_ALEN);
                         }
+                        neigh_node_free_ref(router);
                 }
                 rcu_read_unlock();
         }
@@ -605,7 +610,7 @@ static int generate_vis_packet(struct bat_priv *bat_priv)
         struct hlist_node *node;
         struct hlist_head *head;
         struct orig_node *orig_node;
-        struct neigh_node *neigh_node;
+        struct neigh_node *router;
         struct vis_info *info = (struct vis_info *)bat_priv->my_vis_info;
         struct vis_packet *packet = (struct vis_packet *)info->skb_packet->data;
         struct vis_info_entry *entry;
@@ -633,30 +638,32 @@ static int generate_vis_packet(struct bat_priv *bat_priv)
 
                 rcu_read_lock();
                 hlist_for_each_entry_rcu(orig_node, node, head, hash_entry) {
-                        neigh_node = orig_node->router;
-
-                        if (!neigh_node)
+                        router = orig_node_get_router(orig_node);
+                        if (!router)
                                 continue;
 
-                        if (!compare_eth(neigh_node->addr, orig_node->orig))
-                                continue;
+                        if (!compare_eth(router->addr, orig_node->orig))
+                                goto next;
 
-                        if (neigh_node->if_incoming->if_status != IF_ACTIVE)
-                                continue;
+                        if (router->if_incoming->if_status != IF_ACTIVE)
+                                goto next;
 
-                        if (neigh_node->tq_avg < 1)
-                                continue;
+                        if (router->tq_avg < 1)
+                                goto next;
 
                         /* fill one entry into buffer. */
                         entry = (struct vis_info_entry *)
                                       skb_put(info->skb_packet, sizeof(*entry));
                         memcpy(entry->src,
-                               neigh_node->if_incoming->net_dev->dev_addr,
+                               router->if_incoming->net_dev->dev_addr,
                                ETH_ALEN);
                         memcpy(entry->dest, orig_node->orig, ETH_ALEN);
-                        entry->quality = neigh_node->tq_avg;
+                        entry->quality = router->tq_avg;
                         packet->entries++;
 
+next:
+                        neigh_node_free_ref(router);
+
                         if (vis_packet_full(info))
                                 goto unlock;
                 }
@@ -725,6 +732,7 @@ static void purge_vis_packets(struct bat_priv *bat_priv)
 static void broadcast_vis_packet(struct bat_priv *bat_priv,
                                  struct vis_info *info)
 {
+        struct neigh_node *router;
         struct hashtable_t *hash = bat_priv->orig_hash;
         struct hlist_node *node;
         struct hlist_head *head;
@@ -745,19 +753,26 @@ static void broadcast_vis_packet(struct bat_priv *bat_priv,
                 rcu_read_lock();
                 hlist_for_each_entry_rcu(orig_node, node, head, hash_entry) {
                         /* if it's a vis server and reachable, send it. */
-                        if ((!orig_node) || (!orig_node->router))
-                                continue;
                         if (!(orig_node->flags & VIS_SERVER))
                                 continue;
+
+                        router = orig_node_get_router(orig_node);
+                        if (!router)
+                                continue;
+
                         /* don't send it if we already received the packet from
-                        * this node. */
+                         * this node. */
                         if (recv_list_is_in(bat_priv, &info->recv_list,
-                                            orig_node->orig))
+                                            orig_node->orig)) {
+                                neigh_node_free_ref(router);
                                 continue;
+                        }
 
                         memcpy(packet->target_orig, orig_node->orig, ETH_ALEN);
-                        hard_iface = orig_node->router->if_incoming;
-                        memcpy(dstaddr, orig_node->router->addr, ETH_ALEN);
+                        hard_iface = router->if_incoming;
+                        memcpy(dstaddr, router->addr, ETH_ALEN);
+
+                        neigh_node_free_ref(router);
 
                         skb = skb_clone(info->skb_packet, GFP_ATOMIC);
                         if (skb)
@@ -772,45 +787,29 @@ static void unicast_vis_packet(struct bat_priv *bat_priv,
                                struct vis_info *info)
 {
         struct orig_node *orig_node;
-        struct neigh_node *neigh_node = NULL;
+        struct neigh_node *router = NULL;
         struct sk_buff *skb;
         struct vis_packet *packet;
 
         packet = (struct vis_packet *)info->skb_packet->data;
 
-        rcu_read_lock();
         orig_node = orig_hash_find(bat_priv, packet->target_orig);
-
         if (!orig_node)
-                goto unlock;
+                goto out;
 
-        neigh_node = orig_node->router;
-
-        if (!neigh_node)
-                goto unlock;
-
-        if (!atomic_inc_not_zero(&neigh_node->refcount)) {
-                neigh_node = NULL;
-                goto unlock;
-        }
-
-        rcu_read_unlock();
+        router = orig_node_get_router(orig_node);
+        if (!router)
+                goto out;
 
         skb = skb_clone(info->skb_packet, GFP_ATOMIC);
         if (skb)
-                send_skb_packet(skb, neigh_node->if_incoming,
-                                neigh_node->addr);
-
-        goto out;
+                send_skb_packet(skb, router->if_incoming, router->addr);
 
-unlock:
-        rcu_read_unlock();
 out:
-        if (neigh_node)
-                neigh_node_free_ref(neigh_node);
+        if (router)
+                neigh_node_free_ref(router);
         if (orig_node)
                 orig_node_free_ref(orig_node);
-        return;
 }
 
 /* only send one vis packet. called from send_vis_packets() */