netdev - Re: [RFC PATCH v2 1/2] NET: Clone the sk_buff 'iif' field in __skb

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Date:	Tue, 8 Jan 2008 08:11:11 +1100 (EST)
From:	James Morris <jmorris@...ei.org>
To:	Paul Moore <paul.moore@...com>
cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [RFC PATCH v2 1/2] NET: Clone the sk_buff 'iif' field in
 __skb_clone()

On Mon, 7 Jan 2008, Paul Moore wrote:

> Both NetLabel and SELinux (other LSMs may grow to use it as well) rely on the
> 'iif' field to determine the receiving network interface of inbound packets.
> Unfortunately, at present this field is not preserved across a skb clone
> operation which can lead to garbage values if the cloned skb is sent back
> through the network stack.  This patch corrects this problem by properly
> copying the 'iif' field in __skb_clone() and removing the 'iif' field
> assignment from skb_act_clone() since it is no longer needed.
> 
> Also, while we are here, put the assignments in the same order as the offsets
> to reduce cacheline bounces.
> 
> Signed-off-by: Paul Moore <paul.moore@...com>

Dave, perhaps this one should pushed to Linus now as a bugfix?

> ---
> 
>  include/net/sch_generic.h |    1 -
>  net/core/skbuff.c         |   11 ++++++-----
>  2 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
> index c926551..4c3b351 100644
> --- a/include/net/sch_generic.h
> +++ b/include/net/sch_generic.h
> @@ -325,7 +325,6 @@ static inline struct sk_buff *skb_act_clone(struct sk_buff *skb, gfp_t gfp_mask)
>  		n->tc_verd = SET_TC_VERD(n->tc_verd, 0);
>  		n->tc_verd = CLR_TC_OK2MUNGE(n->tc_verd);
>  		n->tc_verd = CLR_TC_MUNGED(n->tc_verd);
> -		n->iif = skb->iif;
>  	}
>  	return n;
>  }
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 5b4ce9b..b628377 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -416,16 +416,17 @@ static struct sk_buff *__skb_clone(struct sk_buff *n, struct sk_buff *skb)
>  	C(len);
>  	C(data_len);
>  	C(mac_len);
> -	n->cloned = 1;
>  	n->hdr_len = skb->nohdr ? skb_headroom(skb) : skb->hdr_len;
> +	n->cloned = 1;
>  	n->nohdr = 0;
>  	n->destructor = NULL;
> -	C(truesize);
> -	atomic_set(&n->users, 1);
> -	C(head);
> -	C(data);
> +	C(iif);
>  	C(tail);
>  	C(end);
> +	C(head);
> +	C(data);
> +	C(truesize);
> +	atomic_set(&n->users, 1);
>  
>  	atomic_inc(&(skb_shinfo(skb)->dataref));
>  	skb->cloned = 1;
> 
> --
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> 

-- 
James Morris
<jmorris@...ei.org>
--
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