Re: [PATCH] bridge: don't try to update timers in case of broken MLD queries

Linus Lüssing
2013-08-06T00:32:37Z

On Mon, Aug 05, 2013 at 03:42:22PM -0700, Stephen Hemminger wrote:
> On Tue, 6 Aug 2013 00:32:05 +0200
> Linus Lüssing <linus.luessing@web.de> wrote:
>
> > Currently we are reading an uninitialized value for the max_delay
> > variable when snooping an MLD query message of invalid length and would
> > update our timers with that.
> >
> > Fixing this by simply ignoring such broken MLD queries (just like we do
> > for IGMP already).
> >
> > This is a regression introduced by:
> > "bridge: disable snooping if there is no querier" (b00589af3b04)
> >
> > Reported-by: Paul Bolle <pebolle@tiscali.nl>
> > Signed-off-by: Linus Lüssing <linus.luessing@web.de>
> > ---
> > net/bridge/br_multicast.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
> > index 61c5e81..08e576a 100644
> > --- a/net/bridge/br_multicast.c
> > +++ b/net/bridge/br_multicast.c
> > @@ -1195,7 +1195,7 @@ static int br_ip6_multicast_query(struct net_bridge *br,
> > max_delay = msecs_to_jiffies(ntohs(mld->mld_maxdelay));
> > if (max_delay)
> > group = &mld->mld_mca;
> > - } else if (skb->len >= sizeof(*mld2q)) {
> > + } else {
> > if (!pskb_may_pull(skb, sizeof(*mld2q))) {
> > err = -EINVAL;
> > goto out;
>
> Why not use else if here, other than that looks great.

Because it isn't really necessary, it is basically included
in the pskb_may_pull() already, just like it is in the according IGMP
code path.

And I thought it'd be nicer to handle it the same way as in the
IGMP code path to avoid diverging too much.

Cheers, Linus