[B.A.T.M.A.N.] [PATCH 10/14] batman-adv: protect tt_local_entry from concurrent delete events

Antonio Quartulli
2015-08-04T16:35:30Z

From: 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.

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>
---
net/batman-adv/translation-table.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 2db3093..cb2a2d1 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -1038,6 +1038,7 @@ 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)
@@ -1065,7 +1066,15 @@ 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 */
--
2.5.0