[net] nsh: set mac len based on inner packet

Message ID 20180711160046.198091-1-willemdebruijn.kernel@gmail.com
State Accepted
Delegated to: David Miller
Headers show
Series
  • [net] nsh: set mac len based on inner packet
Related show

Commit Message

Willem de Bruijn July 11, 2018, 4 p.m.
From: Willem de Bruijn <willemb@google.com>

When pulling the NSH header in nsh_gso_segment, set the mac length
based on the encapsulated packet type.

skb_reset_mac_len computes an offset to the network header, which
here still points to the outer packet:

  >     skb_reset_network_header(skb);
  >     [...]
  >     __skb_pull(skb, nsh_len);
  >     skb_reset_mac_header(skb);    // now mac hdr starts nsh_len == 8B after net hdr
  >     skb_reset_mac_len(skb);       // mac len = net hdr - mac hdr == (u16) -8 == 65528
  >     [..]
  >     skb_mac_gso_segment(skb, ..)

Link: http://lkml.kernel.org/r/CAF=yD-KeAcTSOn4AxirAxL8m7QAS8GBBe1w09eziYwvPbbUeYA@mail.gmail.com
Reported-by: syzbot+7b9ed9872dab8c32305d@syzkaller.appspotmail.com
Fixes: c411ed854584 ("nsh: add GSO support")
Signed-off-by: Willem de Bruijn <willemb@google.com>
---
 net/nsh/nsh.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Jiri Benc July 12, 2018, 7:28 a.m. | #1
On Wed, 11 Jul 2018 12:00:44 -0400, Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@google.com>
> 
> When pulling the NSH header in nsh_gso_segment, set the mac length
> based on the encapsulated packet type.
> 
> skb_reset_mac_len computes an offset to the network header, which
> here still points to the outer packet:
> 
>   >     skb_reset_network_header(skb);
>   >     [...]
>   >     __skb_pull(skb, nsh_len);
>   >     skb_reset_mac_header(skb);    // now mac hdr starts nsh_len == 8B after net hdr
>   >     skb_reset_mac_len(skb);       // mac len = net hdr - mac hdr == (u16) -8 == 65528
>   >     [..]
>   >     skb_mac_gso_segment(skb, ..)  
> 
> Link: http://lkml.kernel.org/r/CAF=yD-KeAcTSOn4AxirAxL8m7QAS8GBBe1w09eziYwvPbbUeYA@mail.gmail.com
> Reported-by: syzbot+7b9ed9872dab8c32305d@syzkaller.appspotmail.com
> Fixes: c411ed854584 ("nsh: add GSO support")
> Signed-off-by: Willem de Bruijn <willemb@google.com>

Acked-by: Jiri Benc <jbenc@redhat.com>
David Miller July 12, 2018, 11:57 p.m. | #2
From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: Wed, 11 Jul 2018 12:00:44 -0400

> From: Willem de Bruijn <willemb@google.com>
> 
> When pulling the NSH header in nsh_gso_segment, set the mac length
> based on the encapsulated packet type.
> 
> skb_reset_mac_len computes an offset to the network header, which
> here still points to the outer packet:
> 
>   >     skb_reset_network_header(skb);
>   >     [...]
>   >     __skb_pull(skb, nsh_len);
>   >     skb_reset_mac_header(skb);    // now mac hdr starts nsh_len == 8B after net hdr
>   >     skb_reset_mac_len(skb);       // mac len = net hdr - mac hdr == (u16) -8 == 65528
>   >     [..]
>   >     skb_mac_gso_segment(skb, ..)
> 
> Link: http://lkml.kernel.org/r/CAF=yD-KeAcTSOn4AxirAxL8m7QAS8GBBe1w09eziYwvPbbUeYA@mail.gmail.com
> Reported-by: syzbot+7b9ed9872dab8c32305d@syzkaller.appspotmail.com
> Fixes: c411ed854584 ("nsh: add GSO support")
> Signed-off-by: Willem de Bruijn <willemb@google.com>

Applied and queued up for -stable.

Patch

diff --git a/net/nsh/nsh.c b/net/nsh/nsh.c
index 9696ef96b719..1a30e165eeb4 100644
--- a/net/nsh/nsh.c
+++ b/net/nsh/nsh.c
@@ -104,7 +104,7 @@  static struct sk_buff *nsh_gso_segment(struct sk_buff *skb,
 	__skb_pull(skb, nsh_len);
 
 	skb_reset_mac_header(skb);
-	skb_reset_mac_len(skb);
+	skb->mac_len = proto == htons(ETH_P_TEB) ? ETH_HLEN : 0;
 	skb->protocol = proto;
 
 	features &= NETIF_F_SG;