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>
diff --git a/net/batman-adv/originator.c b/net/batman-adv/originator.c
index bdcb399..a70debe 100644
--- a/net/batman-adv/originator.c
+++ b/net/batman-adv/originator.c
@@ -102,13 +102,13 @@
return neigh_node;
}
-void orig_node_free_ref(struct kref *refcount)
+static void orig_node_free_rcu(struct rcu_head *rcu)
{
struct hlist_node *node, *node_tmp;
struct neigh_node *neigh_node, *tmp_neigh_node;
struct orig_node *orig_node;
- orig_node = container_of(refcount, struct orig_node, refcount);
+ orig_node = container_of(rcu, struct orig_node, rcu);
spin_lock_bh(&orig_node->neigh_list_lock);
@@ -137,6 +137,12 @@
kfree(orig_node);
}
+void orig_node_free_ref(struct orig_node *orig_node)
+{
+ if (atomic_dec_and_test(&orig_node->refcount))
+ call_rcu(&orig_node->rcu, orig_node_free_rcu);
+}
+
void originator_free(struct bat_priv *bat_priv)
{
struct hashtable_t *hash = bat_priv->orig_hash;
@@ -163,7 +169,7 @@
head, hash_entry) {
hlist_del_rcu(node);
- kref_put(&orig_node->refcount, orig_node_free_ref);
+ orig_node_free_ref(orig_node);
}
spin_unlock_bh(list_lock);
}
@@ -196,7 +202,9 @@
spin_lock_init(&orig_node->ogm_cnt_lock);
spin_lock_init(&orig_node->bcast_seqno_lock);
spin_lock_init(&orig_node->neigh_list_lock);
- kref_init(&orig_node->refcount);
+
+ /* extra reference for return */
+ atomic_set(&orig_node->refcount, 2);
orig_node->bat_priv = bat_priv;
memcpy(orig_node->orig, addr, ETH_ALEN);
@@ -229,8 +237,6 @@
if (hash_added < 0)
goto free_bcast_own_sum;
- /* extra reference for return */
- kref_get(&orig_node->refcount);
return orig_node;
free_bcast_own_sum:
kfree(orig_node->bcast_own_sum);
@@ -348,8 +354,7 @@
if (orig_node->gw_flags)
gw_node_delete(bat_priv, orig_node);
hlist_del_rcu(node);
- kref_put(&orig_node->refcount,
- orig_node_free_ref);
+ orig_node_free_ref(orig_node);
continue;
}