batman-adv: Fix reference counting of hardif_neigh_node object for neigh_node

The batadv_neigh_node was specific to a batadv_hardif_neigh_node and held
an implicit reference to it. But this reference was never stored in form of
a pointer in the batadv_neigh_node itself. Instead
batadv_neigh_node_release depends on a consistent state of
hard_iface->neigh_list and that batadv_hardif_neigh_get always returns the
batadv_hardif_neigh_node object which it has a reference for. But
batadv_hardif_neigh_get cannot guarantee that because it is working only
with rcu_read_lock on this list. It can therefore happen that a neigh_addr
is in this list twice or that batadv_hardif_neigh_get cannot find the
batadv_hardif_neigh_node for an neigh_addr due to some other list
operations taking place at the same time.

Instead add a batadv_hardif_neigh_node pointer directly in
batadv_neigh_node which will be used for the reference counter decremented
on release of batadv_neigh_node.

Fixes: cef63419f7db ("batman-adv: add list of unique single hop neighbors per hard-interface")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>

diff --git a/net/batman-adv/originator.c b/net/batman-adv/originator.c
index d52f67a0c057230b4b1dfa66d43594d7f30625ee..c355a824713cd9224e2c705e222c2061cb504b5a 100644 (file)
--- a/net/batman-adv/originator.c
+++ b/net/batman-adv/originator.c
@@ -250,7 +250,6 @@ static void batadv_neigh_node_release(struct kref *ref)
 {
        struct hlist_node *node_tmp;
        struct batadv_neigh_node *neigh_node;
-       struct batadv_hardif_neigh_node *hardif_neigh;
        struct batadv_neigh_ifinfo *neigh_ifinfo;
        struct batadv_algo_ops *bao;
 
@@ -262,13 +261,7 @@ static void batadv_neigh_node_release(struct kref *ref)
                batadv_neigh_ifinfo_put(neigh_ifinfo);
        }
 
-       hardif_neigh = batadv_hardif_neigh_get(neigh_node->if_incoming,
-                                              neigh_node->addr);
-       if (hardif_neigh) {
-               /* batadv_hardif_neigh_get() increases refcount too */
-               batadv_hardif_neigh_put(hardif_neigh);
-               batadv_hardif_neigh_put(hardif_neigh);
-       }
+       batadv_hardif_neigh_put(neigh_node->hardif_neigh);
 
        if (bao->bat_neigh_free)
                bao->bat_neigh_free(neigh_node);
@@ -665,6 +658,10 @@ batadv_neigh_node_new(struct batadv_orig_node *orig_node,
        neigh_node->orig_node = orig_node;
        neigh_node->last_seen = jiffies;
 
+       /* increment unique neighbor refcount */
+       kref_get(&hardif_neigh->refcount);
+       neigh_node->hardif_neigh = hardif_neigh;
+
        /* extra reference for return */
        kref_init(&neigh_node->refcount);
        kref_get(&neigh_node->refcount);
@@ -673,9 +670,6 @@ batadv_neigh_node_new(struct batadv_orig_node *orig_node,
        hlist_add_head_rcu(&neigh_node->list, &orig_node->neigh_list);
        spin_unlock_bh(&orig_node->neigh_list_lock);
 
-       /* increment unique neighbor refcount */
-       kref_get(&hardif_neigh->refcount);
-
        batadv_dbg(BATADV_DBG_BATMAN, orig_node->bat_priv,
                   "Creating new neighbor %pM for orig_node %pM on interface %s\n",
                   neigh_addr, orig_node->orig, hard_iface->net_dev->name);

diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 65afd090ab3ebe310c7101c1aa3cf15074ad4ddf..1e47fbe8bb7b2e9b3ec79c64ef508d7305b5d1a7 100644 (file)
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -433,6 +433,7 @@ struct batadv_hardif_neigh_node {
  * @ifinfo_lock: lock protecting private ifinfo members and list
  * @if_incoming: pointer to incoming hard-interface
  * @last_seen: when last packet via this neighbor was received
+ * @hardif_neigh: hardif_neigh of this neighbor
  * @refcount: number of contexts the object is used
  * @rcu: struct used for freeing in an RCU-safe manner
  */
@@ -444,6 +445,7 @@ struct batadv_neigh_node {
        spinlock_t ifinfo_lock; /* protects ifinfo_list and its members */
        struct batadv_hard_iface *if_incoming;
        unsigned long last_seen;
+       struct batadv_hardif_neigh_node *hardif_neigh;
        struct kref refcount;
        struct rcu_head rcu;
 };