The function batadv_gw_node_add is responsible for adding new gw_node to the gateway_list. It is expecting that the caller already checked that there is not already an entry with the same key or not.
But the lock for the list is only held when the list is really modified. This could lead to duplicated entries because another context could create an entry with the same key between the check and the list manipulation.
The check and the manipulation of the list must therefore be in the same locked code section.
Fixes: bc3538cabac5 ("batman-adv: adding gateway functionality") Signed-off-by: Sven Eckelmann sven@narfation.org Acked-by: Marek Lindner mareklindner@neomailbox.ch --- v2: * added kerneldoc about the locking requirements
net/batman-adv/gateway_client.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c index 8b198ee7..140c61a3 100644 --- a/net/batman-adv/gateway_client.c +++ b/net/batman-adv/gateway_client.c @@ -32,6 +32,7 @@ #include <linux/kernel.h> #include <linux/kref.h> #include <linux/list.h> +#include <linux/lockdep.h> #include <linux/netdevice.h> #include <linux/netlink.h> #include <linux/rculist.h> @@ -348,6 +349,9 @@ void batadv_gw_check_election(struct batadv_priv *bat_priv, * @bat_priv: the bat priv with all the soft interface information * @orig_node: originator announcing gateway capabilities * @gateway: announced bandwidth information + * + * Has to be called with the appropriate locks being acquired + * (gw.list_lock). */ static void batadv_gw_node_add(struct batadv_priv *bat_priv, struct batadv_orig_node *orig_node, @@ -355,6 +359,8 @@ static void batadv_gw_node_add(struct batadv_priv *bat_priv, { struct batadv_gw_node *gw_node;
+ lockdep_assert_held(&bat_priv->gw.list_lock); + if (gateway->bandwidth_down == 0) return;
@@ -369,10 +375,8 @@ static void batadv_gw_node_add(struct batadv_priv *bat_priv, gw_node->bandwidth_down = ntohl(gateway->bandwidth_down); gw_node->bandwidth_up = ntohl(gateway->bandwidth_up);
- spin_lock_bh(&bat_priv->gw.list_lock); kref_get(&gw_node->refcount); hlist_add_head_rcu(&gw_node->list, &bat_priv->gw.gateway_list); - spin_unlock_bh(&bat_priv->gw.list_lock);
batadv_dbg(BATADV_DBG_BATMAN, bat_priv, "Found new gateway %pM -> gw bandwidth: %u.%u/%u.%u MBit\n", @@ -428,11 +432,14 @@ void batadv_gw_node_update(struct batadv_priv *bat_priv, { struct batadv_gw_node *gw_node, *curr_gw = NULL;
+ spin_lock_bh(&bat_priv->gw.list_lock); gw_node = batadv_gw_node_get(bat_priv, orig_node); if (!gw_node) { batadv_gw_node_add(bat_priv, orig_node, gateway); + spin_unlock_bh(&bat_priv->gw.list_lock); goto out; } + spin_unlock_bh(&bat_priv->gw.list_lock);
if (gw_node->bandwidth_down == ntohl(gateway->bandwidth_down) && gw_node->bandwidth_up == ntohl(gateway->bandwidth_up))