Re: [PATCH] net: geneve: modify IP header check in geneve6_xmit_skb

Sabrina Dubroca
2021-04-22T16:04:13Z

2021-04-22, 02:39:42 +0200, Florian Westphal wrote:
> Phillip Potter <phil@philpotter.co.uk> wrote:
> > Modify the check in geneve6_xmit_skb to use the size of a struct iphdr
> > rather than struct ipv6hdr. This fixes two kernel selftest failures
> > introduced by commit 6628ddfec758
> > ("net: geneve: check skb is large enough for IPv4/IPv6 header"), without
> > diminishing the fix provided by that commit.
>
> What errors?
>
> > Reported-by: kernel test robot <oliver.sang@intel.com>
> > Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
> > ---
> > drivers/net/geneve.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
> > index 42f31c681846..a57a5e6f614f 100644
> > --- a/drivers/net/geneve.c
> > +++ b/drivers/net/geneve.c
> > @@ -988,7 +988,7 @@ static int geneve6_xmit_skb(struct sk_buff *skb, struct net_device *dev,
> > __be16 sport;
> > int err;
> >
> > - if (!pskb_network_may_pull(skb, sizeof(struct ipv6hdr)))
> > + if (!pskb_network_may_pull(skb, sizeof(struct iphdr)))
> > return -EINVAL;
>
> Seems this is papering over some bug, this change makes no sense to
> me. Can you please explain this?

I'm not sure the original commit (6628ddfec758 ("net: geneve: check
skb is large enough for IPv4/IPv6 header")) is correct either. GENEVE
isn't limited to carrying IP, I think an ethernet header with not much
else on top should be valid.

--
Sabrina