Re: [PATCH net-next,v2] ipvs: orphan skb on LOCAL_IN path

[Simon Horman <horms@verge.net.au>]

On Thu, Jan 29, 2015 at 01:25:51PM -0800, Alex Gartrell wrote:
> skb->sk can be set in the early_demux path.  This can be problematic, as it
> may be a time-wait socket, which will blow up in the ip6_output path when
> we try to pull out the non-existant pinet6 pointer (the type-punning causes
> that pointer to be garbage).
> 
> This patch orphans the skb if it's not a local socket, so we no longer have
> to worry about running into the time-wait problem from early demux.  It
> does this by checking for dev, which is unset in that path.
> 
> Signed-off-by: Alex Gartrell <agartrell@fb.com>
> ---

Hi Alex,

when you say "blow" what exactly happens? Does the kernel panic?
Assuming this is a bug fix could you provide some information
on when the problem was introduced? The reason is to facilitate
backporting to stable.

Thanks

>  net/netfilter/ipvs/ip_vs_xmit.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c
> index 936fd29..9b8c3c4 100644
> --- a/net/netfilter/ipvs/ip_vs_xmit.c
> +++ b/net/netfilter/ipvs/ip_vs_xmit.c
> @@ -484,6 +484,9 @@ static inline int ip_vs_tunnel_xmit_prepare(struct sk_buff *skb,
>  	if (unlikely(cp->flags & IP_VS_CONN_F_NFCT))
>  		ret = ip_vs_confirm_conntrack(skb);
>  	if (ret == NF_ACCEPT) {
> +		/* orphan on LOCAL_IN */
> +		if (skb->dev)
> +			skb_orphan(skb);
>  		nf_reset(skb);
>  		skb_forward_csum(skb);
>  	}
> @@ -502,6 +505,9 @@ static inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff *skb,
>  	else
>  		ip_vs_update_conntrack(skb, cp, 1);
>  	if (!local) {
> +		/* orphan on LOCAL_IN */
> +		if (skb->dev)
> +			skb_orphan(skb);
>  		skb_forward_csum(skb);
>  		NF_HOOK(pf, NF_INET_LOCAL_OUT, skb, NULL, skb_dst(skb)->dev,
>  			dst_output);
> @@ -520,6 +526,9 @@ static inline int ip_vs_send_or_cont(int pf, struct sk_buff *skb,
>  	if (likely(!(cp->flags & IP_VS_CONN_F_NFCT)))
>  		ip_vs_notrack(skb);
>  	if (!local) {
> +		/* orphan on LOCAL_IN */
> +		if (skb->dev)
> +			skb_orphan(skb);
>  		skb_forward_csum(skb);
>  		NF_HOOK(pf, NF_INET_LOCAL_OUT, skb, NULL, skb_dst(skb)->dev,
>  			dst_output);
> -- 
> Alex Gartrell <agartrell@fb.com>
> 
> --
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