[B.A.T.M.A.N.] [PATCHv2 maint] batman-adv: protect tt_local_entry from concurrent delete events

[Marek Lindner <mareklindner@neomailbox.ch>]

The tt_local_entry deletion performed in batadv_tt_local_remove() was neither
protecting against simultaneous deletes nor checking whether the element was
still part of the list before calling hlist_del_rcu().

Replacing the hlist_del_rcu() call with batadv_hash_remove() provides adequate
protection via hash spinlocks as well as an is-element-still-in-hash check to
avoid 'blind' hash removal.

Reported-by: alfonsname@web.de
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
---
 translation-table.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/translation-table.c b/translation-table.c
index e95a424..fa90a6a 100644
--- a/translation-table.c
+++ b/translation-table.c
@@ -1015,6 +1015,7 @@ uint16_t batadv_tt_local_remove(struct batadv_priv *bat_priv,
 	struct batadv_tt_local_entry *tt_local_entry;
 	uint16_t flags, curr_flags = BATADV_NO_FLAGS;
 	struct batadv_softif_vlan *vlan;
+	void *tt_entry_exists;
 
 	tt_local_entry = batadv_tt_local_hash_find(bat_priv, addr, vid);
 	if (!tt_local_entry)
@@ -1042,7 +1043,15 @@ uint16_t batadv_tt_local_remove(struct batadv_priv *bat_priv,
 	 * immediately purge it
 	 */
 	batadv_tt_local_event(bat_priv, tt_local_entry, BATADV_TT_CLIENT_DEL);
-	hlist_del_rcu(&tt_local_entry->common.hash_entry);
+
+	tt_entry_exists = batadv_hash_remove(bat_priv->tt.local_hash,
+					     batadv_compare_tt,
+					     batadv_choose_tt,
+					     &tt_local_entry->common);
+	if (!tt_entry_exists)
+		goto out;
+
+	/* extra call to free the local tt entry */
 	batadv_tt_local_entry_free_ref(tt_local_entry);
 
 	/* decrease the reference held for this vlan */
-- 
2.1.4