netdev - RE: [PATCH net 1/2] xfrm6: Fix IPv6 payload_len in xfrm6_transport

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Date:   Wed, 21 Jun 2017 15:59:30 +0000
From:   Yossi Kuperman <yossiku@...lanox.com>
To:     Steffen Klassert <steffen.klassert@...unet.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Yevgeny Kliteynik <kliteyn@...lanox.com>,
        Boris Pismenny <borisp@...lanox.com>,
        Ilan Tayari <ilant@...lanox.com>
Subject: RE: [PATCH net 1/2] xfrm6: Fix IPv6 payload_len in
 xfrm6_transport_finish



> -----Original Message-----
> From: Steffen Klassert [mailto:steffen.klassert@...unet.com]
> Sent: Wednesday, June 21, 2017 2:38 PM
> To: Yossi Kuperman <yossiku@...lanox.com>
> Cc: netdev@...r.kernel.org; Herbert Xu <herbert@...dor.apana.org.au>;
> Yevgeny Kliteynik <kliteyn@...lanox.com>; Boris Pismenny
> <borisp@...lanox.com>; Ilan Tayari <ilant@...lanox.com>
> Subject: Re: [PATCH net 1/2] xfrm6: Fix IPv6 payload_len in
> xfrm6_transport_finish
> 
> On Wed, Jun 21, 2017 at 11:24:05AM +0000, Yossi Kuperman wrote:
> >
> >
> > > -----Original Message-----
> > > From: Steffen Klassert [mailto:steffen.klassert@...unet.com]
> > > Sent: Wednesday, June 21, 2017 8:37 AM
> > > To: Yossi Kuperman <yossiku@...lanox.com>
> > > Cc: netdev@...r.kernel.org; Herbert Xu
> > > <herbert@...dor.apana.org.au>; Yevgeny Kliteynik
> > > <kliteyn@...lanox.com>; Boris Pismenny <borisp@...lanox.com>; Ilan
> > > Tayari <ilant@...lanox.com>
> > > Subject: Re: [PATCH net 1/2] xfrm6: Fix IPv6 payload_len in
> > > xfrm6_transport_finish
> > >
> > > On Mon, Jun 19, 2017 at 11:33:20AM +0300, yossiku@...lanox.com
> wrote:
> > > > From: Yossi Kuperman <yossiku@...lanox.com>
> > > >
> > > > IPv6 payload length indicates the size of the payload, including
> > > > any extension headers. In xfrm6_transport_finish,
> > > > ipv6_hdr(skb)->payload_len is set to the payload size only,
> > > > regardless of the presence of any extension headers.
> > > >
> > > > After ESP GRO transport mode decapsulation, ipv6_rcv trims the
> > > > packet according to the wrong payload_len, thus corrupting the packet.
> > > >
> > > > Set payload_len to account for extension headers as well.
> > > >
> > > > Fixes: 716062fd4c2f ("[IPSEC]: Merge most of the input path")
> > > > Signed-off-by: Yossi Kuperman <yossiku@...lanox.com>
> > > > ---
> > > >  net/ipv6/xfrm6_input.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/net/ipv6/xfrm6_input.c b/net/ipv6/xfrm6_input.c index
> > > > 08a807b..3ef5d91 100644
> > > > --- a/net/ipv6/xfrm6_input.c
> > > > +++ b/net/ipv6/xfrm6_input.c
> > > > @@ -43,8 +43,8 @@ int xfrm6_transport_finish(struct sk_buff *skb,
> > > > int
> > > async)
> > > >  		return 1;
> > > >  #endif
> > > >
> > > > -	ipv6_hdr(skb)->payload_len = htons(skb->len);
> > > >  	__skb_push(skb, skb->data - skb_network_header(skb));
> > > > +	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct
> > > > +ipv6hdr));
> > >
> > > You mentioned that the bug happens with ESP GRO. Does this bug also
> > > happen in the standard codepath? If not, you might better move the
> > > above line into the 'if' section below.
> > >
> >
> > Yes, it happens only with ESP GRO.
> 
> In this case your Fixes tag is wrong.
> 
> > Normally, ipv6_rcv happens first which trims the packet correctly and then
> comes xfrm6_transport_finish.
> > Now, with ESP GRO introduced, xfrm6_transport_finish, which comes
> > first, modifies the packet's payload_len, and followed by a call to ipv6_rcv
> which trims it wrongly.
> >
> > If I understand you right, you suggest to move the new line under the "if"
> section and restore the removed line?
> 
> I just want to make sure that the standard codepath works with this cange.
> Did you test this with the standard codepath too?

Sure, it works when GRO is disabled (esp6_offload is not loaded).
Tested: ping, iperf (TCP stream) and injected manually created packets with extension headers.