Re: [PATCH 2/2] ip_tunnel: Add missing validation of encap type to ip_tunnel_encap_setup()

[Thomas Graf <tgraf@suug.ch>]

On 12/16/14 at 12:23pm, Tom Herbert wrote:
> On Tue, Dec 16, 2014 at 12:05 PM, Thomas Graf <tgraf@suug.ch> wrote:
> > The encap->type comes straight from Netlink. Validate it against
> > max supported encap types just like ip_encap_hlen() already does.
> >
> > Fixes: a8c5f9 ("ip_tunnel: Ops registration for secondary encap (fou, gue)")
> > Signed-off-by: Thomas Graf <tgraf@suug.ch>
> > ---
> >  net/ipv4/ip_tunnel.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
> > index 2f498f8..d3e4479 100644
> > --- a/net/ipv4/ip_tunnel.c
> > +++ b/net/ipv4/ip_tunnel.c
> > @@ -573,6 +573,9 @@ int ip_tunnel_encap(struct sk_buff *skb, struct ip_tunnel *t,
> >         if (t->encap.type == TUNNEL_ENCAP_NONE)
> >                 return 0;
> >
> > +       if (t->encap.type >= MAX_IPTUN_ENCAP_OPS)
> > +               return -EINVAL;
> > +
> 
> I don't think this is technically needed, we should have already
> verified the type when setting up the tunnel (ip_encap_hlen).

Right, assuming that every API user always calls ip_tunnel_encap_setup()
on changelink. It's currently the case but since this is a exported
API I figured we better be safe than sorry, in particular as
ip_tunnel_encap() is called before ip_encap_hlen() on xmit.