batman-adv: Fix multicast TT issues with bogus ROAM flags

commit a44ebeff6bbd6ef50db41b4195fca87b21aefd20 upstream.

When a (broken) node wrongly sends multicast TT entries with a ROAM
flag then this causes any receiving node to drop all entries for the
same multicast MAC address announced by other nodes, leading to
packet loss.

Fix this DoS vector by only storing TT sync flags. For multicast TT
non-sync'ing flag bits like ROAM are unused so far anyway.

Fixes: 1d8ab8d3c176 ("batman-adv: Modified forwarding behaviour for multicast packets")
Reported-by: Leonardo Mörlein <me@irrelefant.net>
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
[ bp: 4.4 backported: adjust context, use old style to access flags ]
Signed-off-by: Sven Eckelmann <sven@narfation.org>
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 1ad90267064dc572e233d4f385ecfe6fc3c5c070..1e71e0c9b47b2d867221cc4602c8e29002ed25aa 100644 (file)
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -1426,7 +1426,8 @@ static bool batadv_tt_global_add(struct batadv_priv *bat_priv,
                ether_addr_copy(common->addr, tt_addr);
                common->vid = vid;
 
-               common->flags = flags & (~BATADV_TT_SYNC_MASK);
+               if (!is_multicast_ether_addr(common->addr))
+                       common->flags = flags & (~BATADV_TT_SYNC_MASK);
 
                tt_global_entry->roam_at = 0;
                /* node must store current time in case of roaming. This is
@@ -1489,7 +1490,8 @@ static bool batadv_tt_global_add(struct batadv_priv *bat_priv,
                 * TT_CLIENT_WIFI, therefore they have to be copied in the
                 * client entry
                 */
-               tt_global_entry->common.flags |= flags & (~BATADV_TT_SYNC_MASK);
+               if (!is_multicast_ether_addr(common->addr))
+                       tt_global_entry->common.flags |= flags & (~BATADV_TT_SYNC_MASK);
 
                /* If there is the BATADV_TT_CLIENT_ROAM flag set, there is only
                 * one originator left in the list and we previously received a