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authorAntonio Quartulli <antonio@open-mesh.com>2014-01-29 11:25:12 +0100
committerAntonio Quartulli <antonio@meshcoding.com>2014-02-17 17:17:01 +0100
commit08bf0ed29c7ded45c477d08618220dd200c3524a (patch)
tree102dc9b539fb06435727c592c720d17fc62ddbb9 /net/batman-adv
parentf1791425cf0bcda43ab9a9a37df1ad3ccb1f6654 (diff)
batman-adv: avoid potential race condition when adding a new neighbour
When adding a new neighbour it is important to atomically perform the following: - check if the neighbour already exists - append the neighbour to the proper list If the two operations are not performed in an atomic context it is possible that two concurrent insertions add the same neighbour twice. Signed-off-by: Antonio Quartulli <antonio@open-mesh.com> Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Diffstat (limited to 'net/batman-adv')
-rw-r--r--net/batman-adv/bat_iv_ogm.c22
-rw-r--r--net/batman-adv/originator.c36
-rw-r--r--net/batman-adv/originator.h4
3 files changed, 56 insertions, 6 deletions
diff --git a/net/batman-adv/bat_iv_ogm.c b/net/batman-adv/bat_iv_ogm.c
index 512159bf607f..094ae7ca50a0 100644
--- a/net/batman-adv/bat_iv_ogm.c
+++ b/net/batman-adv/bat_iv_ogm.c
@@ -266,7 +266,7 @@ batadv_iv_ogm_neigh_new(struct batadv_hard_iface *hard_iface,
struct batadv_orig_node *orig_neigh)
{
struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);
- struct batadv_neigh_node *neigh_node;
+ struct batadv_neigh_node *neigh_node, *tmp_neigh_node;
neigh_node = batadv_neigh_node_new(hard_iface, neigh_addr, orig_node);
if (!neigh_node)
@@ -281,14 +281,24 @@ batadv_iv_ogm_neigh_new(struct batadv_hard_iface *hard_iface,
neigh_node->orig_node = orig_neigh;
neigh_node->if_incoming = hard_iface;
- batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
- "Creating new neighbor %pM for orig_node %pM on interface %s\n",
- neigh_addr, orig_node->orig, hard_iface->net_dev->name);
-
spin_lock_bh(&orig_node->neigh_list_lock);
- hlist_add_head_rcu(&neigh_node->list, &orig_node->neigh_list);
+ tmp_neigh_node = batadv_neigh_node_get(orig_node, hard_iface,
+ neigh_addr);
+ if (!tmp_neigh_node) {
+ hlist_add_head_rcu(&neigh_node->list, &orig_node->neigh_list);
+ } else {
+ kfree(neigh_node);
+ batadv_hardif_free_ref(hard_iface);
+ neigh_node = tmp_neigh_node;
+ }
spin_unlock_bh(&orig_node->neigh_list_lock);
+ if (!tmp_neigh_node)
+ batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
+ "Creating new neighbor %pM for orig_node %pM on interface %s\n",
+ neigh_addr, orig_node->orig,
+ hard_iface->net_dev->name);
+
out:
return neigh_node;
}
diff --git a/net/batman-adv/originator.c b/net/batman-adv/originator.c
index 6df12a2e3605..853941629dc1 100644
--- a/net/batman-adv/originator.c
+++ b/net/batman-adv/originator.c
@@ -458,6 +458,42 @@ out:
}
/**
+ * batadv_neigh_node_get - retrieve a neighbour from the list
+ * @orig_node: originator which the neighbour belongs to
+ * @hard_iface: the interface where this neighbour is connected to
+ * @addr: the address of the neighbour
+ *
+ * Looks for and possibly returns a neighbour belonging to this originator list
+ * which is connected through the provided hard interface.
+ * Returns NULL if the neighbour is not found.
+ */
+struct batadv_neigh_node *
+batadv_neigh_node_get(const struct batadv_orig_node *orig_node,
+ const struct batadv_hard_iface *hard_iface,
+ const uint8_t *addr)
+{
+ struct batadv_neigh_node *tmp_neigh_node, *res = NULL;
+
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(tmp_neigh_node, &orig_node->neigh_list, list) {
+ if (!batadv_compare_eth(tmp_neigh_node->addr, addr))
+ continue;
+
+ if (tmp_neigh_node->if_incoming != hard_iface)
+ continue;
+
+ if (!atomic_inc_not_zero(&tmp_neigh_node->refcount))
+ continue;
+
+ res = tmp_neigh_node;
+ break;
+ }
+ rcu_read_unlock();
+
+ return res;
+}
+
+/**
* batadv_orig_ifinfo_free_rcu - free the orig_ifinfo object
* @rcu: rcu pointer of the orig_ifinfo object
*/
diff --git a/net/batman-adv/originator.h b/net/batman-adv/originator.h
index 37be290f63f6..db3a9ed734cb 100644
--- a/net/batman-adv/originator.h
+++ b/net/batman-adv/originator.h
@@ -29,6 +29,10 @@ void batadv_orig_node_free_ref_now(struct batadv_orig_node *orig_node);
struct batadv_orig_node *batadv_orig_node_new(struct batadv_priv *bat_priv,
const uint8_t *addr);
struct batadv_neigh_node *
+batadv_neigh_node_get(const struct batadv_orig_node *orig_node,
+ const struct batadv_hard_iface *hard_iface,
+ const uint8_t *addr);
+struct batadv_neigh_node *
batadv_neigh_node_new(struct batadv_hard_iface *hard_iface,
const uint8_t *neigh_addr,
struct batadv_orig_node *orig_node);

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