netdev - Re: [PATCH 2/2] vlan: adjust vlan_set_encap

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Message-ID: <CAEP_g=_eWXuR_3zUYsbBiAjaCJQjRpSmUypqpJe5_jwN=rmM0Q@mail.gmail.com>
Date:	Fri, 22 Feb 2013 17:05:01 -0800
From:	Jesse Gross <jesse@...ira.com>
To:	Cong Wang <amwang@...hat.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 2/2] vlan: adjust vlan_set_encap_proto() for its callers

On Fri, Feb 22, 2013 at 1:32 AM, Cong Wang <amwang@...hat.com> wrote:
> From: Cong Wang <amwang@...hat.com>
>
> There are two places to call vlan_set_encap_proto():
> vlan_untag() and __pop_vlan_tci().
>
> vlan_untag() assumes skb->data points after mac addr, otherwise
> the following code
>
>         vhdr = (struct vlan_hdr *) skb->data;
>         vlan_tci = ntohs(vhdr->h_vlan_TCI);
>         __vlan_hwaccel_put_tag(skb, vlan_tci);
>
>         skb_pull_rcsum(skb, VLAN_HLEN);
>
> won't be correct. But __pop_vlan_tci() assumes points _before_
> mac addr.
>
> In vlan_set_encap_proto(), it looks for some magic L2 value
> after mac addr:
>
>         rawp = skb->data;
>         if (*(unsigned short *) rawp == 0xFFFF)
>         ...
>
> Therefore __pop_vlan_tci() is obviously wrong.
>
> A quick fix is avoiding using skb->data in vlan_set_encap_proto(),
> use 'vhdr+1' is always correct in both cases.
>
> Cc: David S. Miller <davem@...emloft.net>
> Cc: Jesse Gross <jesse@...ira.com>
> Signed-off-by: Cong Wang <amwang@...hat.com>

Acked-by: Jesse Gross <jesse@...ira.com>
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