[PATCH 4.9 69/90] batman-adv: Fix multicast TT issues with bogus ROAM flags

[Greg Kroah-Hartman]

From: Linus Lü <linus.luessing@xxxxxxxxx>

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 Möin <me@xxxxxxxxxxxxxx>
Signed-off-by: Linus Lü <linus.luessing@xxxxxxxxx>
Signed-off-by: Simon Wunderlich <sw@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/batman-adv/translation-table.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -1708,7 +1708,8 @@ static bool batadv_tt_global_add(struct
 		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
@@ -1772,7 +1773,8 @@ static bool batadv_tt_global_add(struct
 		 * TT_CLIENT_TEMP, therefore they have to be copied in the
 		 * client entry
 		 */
-		common->flags |= flags & (~BATADV_TT_SYNC_MASK);
+		if (!is_multicast_ether_addr(common->addr))
+			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