[Bridge] [PATCH net 1/2] bridge: Avoid infinite loop when suppressing NS messages with invalid options
Nikolay Aleksandrov
nikolay at cumulusnetworks.com
Mon Jun 1 13:02:16 UTC 2020
On 01/06/2020 15:58, Ido Schimmel wrote:
> From: Ido Schimmel <idosch at mellanox.com>
>
> 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 at mellanox.com>
> Reported-by: Alla Segal <allas at mellanox.com>
> Tested-by: Alla Segal <allas at mellanox.com>
> ---
> net/bridge/br_arp_nd_proxy.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/net/bridge/br_arp_nd_proxy.c b/net/bridge/br_arp_nd_proxy.c
> index 37908561a64b..b18cdf03edb3 100644
> --- 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;
>
Good catch!
Acked-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
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