[B.A.T.M.A.N.] [PATCH 4/4] batman-adv: Fix reference counting of hardif_neigh_node object for neigh_node

Antonio Quartulli
2016-04-30T17:06:03Z

From: Sven Eckelmann <sven@narfation.org>

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>
---
net/batman-adv/originator.c | 16 +++++-----------
net/batman-adv/types.h | 2 ++
2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/net/batman-adv/originator.c b/net/batman-adv/originator.c
index d52f67a0c057..c355a824713c 100644
--- 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 65afd090ab3e..1e47fbe8bb7b 100644
--- 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;
};
--
2.8.1