batman-adv: protect tt_local_entry from concurrent delete events

commit ef72706a0543d0c3a5ab29bd6378fdfb368118d9 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index d41537cb867bedcb85a6b8c91ccdd29876129c6d..deb87c6870aaa10a56f56bfb2a43dc96fea1c64f 100644 (file)
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -1018,6 +1018,7 @@ 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)
@@ -1045,7 +1046,15 @@ 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 */