On Tue, Mar 04, 2014 at 03:57:35AM +0100, Linus Lüssing wrote:
> MLD queries are supposed to have an IPv6 link-local source address
> according to RFC2710, section 4 and RFC3810, section 5.1.14. This patch
> adds a sanity check to ignore such broken MLD queries.
>
> Without this check, such malformed MLD queries can result in a
> denial of service: The queries are ignored by any MLD listener
> therefore they will not respond with an MLD report. However,
> without this patch these malformed MLD queries would enable the
> snooping part in the bridge code, potentially shutting down the
> according ports towards these hosts for multicast traffic as the
> bridge did not learn about these listeners.
>
> Reported-by: Jan Stancek <jstancek@xxxxxxxxxx>
> Signed-off-by: Linus Lüssing <linus.luessing@xxxxxx>
> ---
> net/bridge/br_multicast.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
> index ef66365..fb0e36f 100644
> --- a/net/bridge/br_multicast.c
> +++ b/net/bridge/br_multicast.c
> @@ -1235,6 +1235,12 @@ static int br_ip6_multicast_query(struct net_bridge *br,
> (port && port->state == BR_STATE_DISABLED))
> goto out;
>
> + /* RFC2710+RFC3810 (MLDv1+MLDv2) require link-local source addresses */
> + if (!(ipv6_addr_type(&ip6h->saddr) & IPV6_ADDR_LINKLOCAL)) {
> + err = -EINVAL;
> + goto out;
> + }
> +
Shouldn't we allow empty source address, here?
Routers are supposed to drop them but bridges care. Linux uses ::
as source address as long as no valid LL addresses are available,
e.g. at boot-up (RFC3810 5.2.13.).
Greetings,
Hannes
