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batman-adv: Only put gw_node list reference when removed 

The batadv_gw_node reference counter in batadv_gw_node_update can only be
reduced when the list entry was actually removed. Otherwise the reference
counter may reach zero when batadv_gw_node_update is called from two
different contexts for the same gw_node but only one context is actually
removing the entry from the list.

The release function for this gw_node is not called inside the list_lock
spinlock protected region because the function batadv_gw_node_update still
holds a gw_node reference for the object pointer on the stack. Thus the
actual release function (when required) will be called only at the end of
the function.

Fixes: bd3524c14b ("batman-adv: remove obsolete deleted attribute for gateway node")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>
This commit is contained in:
Sven Eckelmann 2016-01-31 13:27:59 +01:00 committed by Antonio Quartulli
parent db92ea5d4d
commit c18bdd018e
1 changed files with 4 additions and 3 deletions
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7
net/batman-adv/gateway_client.c
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@ -527,11 +527,12 @@ void batadv_gw_node_update(struct batadv_priv *bat_priv,
* gets dereferenced.
*/
spin_lock_bh(&bat_priv->gw.list_lock);
hlist_del_init_rcu(&gw_node->list);
if (!hlist_unhashed(&gw_node->list)) {
hlist_del_init_rcu(&gw_node->list);
batadv_gw_node_free_ref(gw_node);
}
spin_unlock_bh(&bat_priv->gw.list_lock);
batadv_gw_node_free_ref(gw_node);
curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
if (gw_node == curr_gw)
batadv_gw_reselect(bat_priv);