batman-adv: Do not send uninitialized TT changes

The number of TT changes can be less than initially expected in
batadv_tt_tvlv_container_update() (changes can be removed by
batadv_tt_local_event() in ADD+DEL sequence between reading
tt_diff_entries_num and actually iterating the change list under lock).

Thus tt_diff_len could be bigger than the actual changes size that need
to be sent. Because batadv_send_my_tt_response sends the whole
packet, uninitialized data can be interpreted as TT changes on other
nodes leading to weird TT global entries on those nodes such as:

 * 00:00:00:00:00:00   -1 [....] (  0) 88:12:4e:ad:7e:ba (179) (0x45845380)
 * 00:00:00:00:78:79 4092 [.W..] (  0) 88:12:4e:ad:7e:3c (145) (0x8ebadb8b)

All of the above also applies to OGM tvlv container buffer's tvlv_len.

Remove the extra allocated space to avoid sending uninitialized TT
changes in batadv_send_my_tt_response() and batadv_v_ogm_send_softif().

Fixes: e1bf0c1 ("batman-adv: tvlv - convert tt data sent within OGMs")
Signed-off-by: Remi Pommarel <[email protected]>
Signed-off-by: Sven Eckelmann <[email protected]>
Signed-off-by: Simon Wunderlich <[email protected]>

Author: repk

net/batman-adv/translation-table.c

@@ -948,6 +948,7 @@ static void batadv_tt_tvlv_container_update(struct batadv_priv *bat_priv)
 	int tt_diff_len, tt_change_len = 0;
 	int tt_diff_entries_num = 0;
 	int tt_diff_entries_count = 0;
+	size_t tt_extra_len = 0;
 	u16 tvlv_len;
 
 	tt_diff_entries_num = atomic_read(&bat_priv->tt.local_changes);
@@ -985,6 +986,9 @@ static void batadv_tt_tvlv_container_update(struct batadv_priv *bat_priv)
 	}
 	spin_unlock_bh(&bat_priv->tt.changes_list_lock);
 
+	tt_extra_len = batadv_tt_len(tt_diff_entries_num -
+				     tt_diff_entries_count);
+
 	/* Keep the buffer for possible tt_request */
 	spin_lock_bh(&bat_priv->tt.last_changeset_lock);
 	kfree(bat_priv->tt.last_changeset);
@@ -993,6 +997,7 @@ static void batadv_tt_tvlv_container_update(struct batadv_priv *bat_priv)
 	tt_change_len = batadv_tt_len(tt_diff_entries_count);
 	/* check whether this new OGM has no changes due to size problems */
 	if (tt_diff_entries_count > 0) {
+		tt_diff_len -= tt_extra_len;
 		/* if kmalloc() fails we will reply with the full table
 		 * instead of providing the diff
 		 */
@@ -1005,6 +1010,8 @@ static void batadv_tt_tvlv_container_update(struct batadv_priv *bat_priv)
 	}
 	spin_unlock_bh(&bat_priv->tt.last_changeset_lock);
 
+	/* Remove extra packet space for OGM */
+	tvlv_len -= tt_extra_len;
 container_register:
 	batadv_tvlv_container_register(bat_priv, BATADV_TVLV_TT, 1, tt_data,
 				       tvlv_len);