batman-adv: Correct rcu refcounting for orig_node

It might be possible that 2 threads access the same data in the same
rcu grace period. The first thread calls call_rcu() to decrement the
refcount and free the data while the second thread increases the
refcount to use the data. To avoid this race condition all refcount
operations have to be atomic.

Reported-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>

1 files changed, 3 insertions, 3 deletions

diff --git a/net/batman-adv/unicast.c b/net/batman-adv/unicast.c
index 2d5daac52034..2ab819841231 100644
--- a/net/batman-adv/unicast.c
+++ b/net/batman-adv/unicast.c
@@ -211,7 +211,7 @@ unlock:
         spin_unlock_bh(&bat_priv->orig_hash_lock);
 out:
         if (orig_node)
-                kref_put(&orig_node->refcount, orig_node_free_ref);
+                orig_node_free_ref(orig_node);
         return ret;
 }
 
@@ -280,7 +280,7 @@ int unicast_send_skb(struct sk_buff *skb, struct bat_priv *bat_priv)
 {
         struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
         struct unicast_packet *unicast_packet;
-        struct orig_node *orig_node = NULL;
+        struct orig_node *orig_node;
         struct batman_if *batman_if;
         struct neigh_node *neigh_node;
         int data_len = skb->len;
@@ -347,7 +347,7 @@ out:
         if (neigh_node)
                 neigh_node_free_ref(neigh_node);
         if (orig_node)
-                kref_put(&orig_node->refcount, orig_node_free_ref);
+                orig_node_free_ref(orig_node);
         if (ret == 1)
                 kfree_skb(skb);
         return ret;