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SubjectRe: [PATCH] ip6_offload: check segs for NULL in ipv6_gso_segment.
On Thu, Dec 01, 2016 at 06:34:07AM -0800, Eric Dumazet wrote:
> On Thu, 2016-12-01 at 14:06 +0100, Artem Savkov wrote:
> > segs needs to be checked for being NULL in ipv6_gso_segment() before calling
> > skb_shinfo(segs), otherwise kernel can run into a NULL-pointer dereference:
>
>
> > Signed-off-by: Artem Savkov <asavkov@redhat.com>
> > ---
> >
>
> > diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
> > index 1fcf61f..89c59e6 100644
> > --- a/net/ipv6/ip6_offload.c
> > +++ b/net/ipv6/ip6_offload.c
> > @@ -99,7 +99,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
> > segs = ops->callbacks.gso_segment(skb, features);
> > }
> >
> > - if (IS_ERR(segs))
> > + if (IS_ERR_OR_NULL(segs))
> > goto out;
> >
> > gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
>
> Do you know when was this bug added ?

It started to show up with 4.9-rc4, from what I see the culprit is
07b26c9 gso: Support partial splitting at the frag_list pointer

> Are you sure this is the right fix ?

I am not, but this would have the same behavior as pre-07b26c9 code and
IS_ERR_OR_NULL is used in ipv4's inet_gso_segment().

> Which gso_segment() is returning NULL exactly ?

Unfortunatelly I don't know that and I don't have a good reproducer, the
only way to reproduce this that I currently have is calling
virt-install.

--
Regards,
Artem

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