[v4] batman-adv: avoid potential race condition when adding a new neighbour
Commit Message
From: Antonio Quartulli <antonio@open-mesh.com>
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>
---
Changes from v3:
- remove useless initialization
Changes from v2:
- fix typ0
Changes from v1:
- release hard_iface if we already have a matching neighbour
bat_iv_ogm.c | 22 ++++++++++++++++------
originator.c | 36 ++++++++++++++++++++++++++++++++++++
originator.h | 4 ++++
3 files changed, 56 insertions(+), 6 deletions(-)
Comments
On Wednesday 29 January 2014 11:25:12 Antonio Quartulli wrote:
> From: Antonio Quartulli <antonio@open-mesh.com>
>
> 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>
> ---
>
> Changes from v3:
> - remove useless initialization
>
> Changes from v2:
> - fix typ0
>
> Changes from v1:
> - release hard_iface if we already have a matching neighbour
>
>
> bat_iv_ogm.c | 22 ++++++++++++++++------
> originator.c | 36 ++++++++++++++++++++++++++++++++++++
> originator.h | 4 ++++
> 3 files changed, 56 insertions(+), 6 deletions(-)
Applied in revision e08e28f.
Thanks,
Marek
@@ -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;
}
@@ -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
*/
@@ -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);