batman-adv: protect tt_local_entry from concurrent delete events

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.

Fixes: 068ee6e204e1 ("batman-adv: roaming handling mechanism redesign")
Reported-by: alfonsname@web.de
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 38b83c50f936..5e953297d3b2 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -1037,6 +1037,7 @@ 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)
@@ -1064,7 +1065,15 @@ 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 */