Re: [PATCH] bridge: netfilter: orphan skb before invoking ip netfilter hooks

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On Thu, 2013-10-24 at 21:32 +0200, Florian Westphal wrote:
> Pekka Pietikäinen reports xt_socket behavioural change after commit

behavioral maybe ? ;)

> 00028aa37098o (netfilter: xt_socket: use IP early demux).
> 
> Reason is xt_socket now no longer does an unconditional sk lookup -
> it re-uses existing skb->sk if possible, assuming ->sk was set by
> tcp early demux.

s/tcp/ip/ since it also can work for UDP sockets in net-next

> 
> However, when netfilter is invoked via bridge, this can cause 'bogus'
> sockets to be examined by the match, e.g. a 'tun' device socket.
> 
> bridge netfilter should orphan the skb just like the routing path
> before invoking ipv4/ipv6 netfilter hooks to avoid this.
> 
> Reported-and-tested-by: Pekka Pietikäinen <pp@xxxxxxxxxx>
> Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
> ---
> diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
> index 878f008..80cad2c 100644
> --- a/net/bridge/br_netfilter.c
> +++ b/net/bridge/br_netfilter.c
> @@ -559,6 +559,8 @@ static struct net_device *setup_pre_routing(struct sk_buff *skb)
>  	else if (skb->protocol == htons(ETH_P_PPP_SES))
>  		nf_bridge->mask |= BRNF_PPPoE;
>  
> +	/* Must drop socket now because of tproxy. */
> +	skb_orphan(skb);
>  	return skb->dev;
>  }
>  

This was a nice one, thanks Florian !

Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>



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