bridge: Avoid infinite loop when suppressing NS messages with invalid options

When neighbor suppression is enabled the bridge device might reply to
Neighbor Solicitation (NS) messages on behalf of remote hosts.

In case the NS message includes the "Source link-layer address" option
[1], the bridge device will use the specified address as the link-layer
destination address in its reply.

To avoid an infinite loop, break out of the options parsing loop when
encountering an option with length zero and disregard the NS message.

This is consistent with the IPv6 ndisc code and RFC 4886 which states
that "Nodes MUST silently discard an ND packet that contains an option
with length zero" [2].

[1] https://tools.ietf.org/html/rfc4861#section-4.3
[2] https://tools.ietf.org/html/rfc4861#section-4.6

Fixes: ed842faeb2bd ("bridge: suppress nd pkts on BR_NEIGH_SUPPRESS ports")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reported-by: Alla Segal <allas@mellanox.com>
Tested-by: Alla Segal <allas@mellanox.com>
Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/bridge/br_arp_nd_proxy.c b/net/bridge/br_arp_nd_proxy.c
index 37908561a64b5c5551d963526b0b39bd8e9a2129..b18cdf03edb35b90244a15387e35d19abc3d44d8 100644 (file)
--- a/net/bridge/br_arp_nd_proxy.c
+++ b/net/bridge/br_arp_nd_proxy.c
@@ -276,6 +276,10 @@ static void br_nd_send(struct net_bridge *br, struct net_bridge_port *p,
        ns_olen = request->len - (skb_network_offset(request) +
                                  sizeof(struct ipv6hdr)) - sizeof(*ns);
        for (i = 0; i < ns_olen - 1; i += (ns->opt[i + 1] << 3)) {
+               if (!ns->opt[i + 1]) {
+                       kfree_skb(reply);
+                       return;
+               }
                if (ns->opt[i] == ND_OPT_SOURCE_LL_ADDR) {
                        daddr = ns->opt + i + sizeof(struct nd_opt_hdr);
                        break;