linux-kernel - Re: [PATCH] Netfilter: Fix an ICMPv6 bug which caused by a latter ICMPv6 NA packet to inherit the mark of previous NS packet.

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Message-ID: <20161021090035.GA32634@breakpoint.cc>
Date:   Fri, 21 Oct 2016 11:00:35 +0200
From:   Florian Westphal <fw@...len.de>
To:     XU Tianwen <evan.xu.tianwen@...il.com>
Cc:     yasuyuki.kozakai@...hiba.co.jp, pablo@...filter.org,
        kaber@...sh.net, kadlec@...ckhole.kfki.hu, davem@...emloft.net,
        kuznet@....inr.ac.ru, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Netfilter: Fix an ICMPv6 bug which caused by a latter
 ICMPv6 NA packet to inherit the mark of previous NS packet.

XU Tianwen <evan.xu.tianwen@...il.com> wrote:
> The root cause is an ICMPv6 packet hits an untracked connection and inherits a mark from the previous packet to which it is not related, IMO it doesn't make sense to inherit mark for nf_conntrack_untracked.
> 
> Signed-off-by: XU Tianwen <evan.xu.tianwen@...il.com>
> ---
>  net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c b/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c
> index f5a61bc..1be9000 100644
> --- a/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c
> +++ b/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c
> @@ -223,6 +223,9 @@ icmpv6_error(struct net *net, struct nf_conn *tmpl,
>  	if (type >= 0 && type < sizeof(noct_valid_new) &&
>  	    noct_valid_new[type]) {
>  		skb->nfct = &nf_ct_untracked_get()->ct_general;
> +#ifdef CONFIG_NF_CONNTRACK_MARK
> +		((struct nf_conn *)skb->nfct)->mark = 0;
> +#endif
>  		skb->nfctinfo = IP_CT_NEW;
>  		nf_conntrack_get(skb->nfct);
>  		return NF_ACCEPT;
> -- 
> 2.1.2

Where does that bogus mark come from in first place?
Untracked mark should always be 0.

Maybe we need this instead?

diff --git a/net/netfilter/xt_connmark.c b/net/netfilter/xt_connmark.c
--- a/net/netfilter/xt_connmark.c
+++ b/net/netfilter/xt_connmark.c
@@ -44,7 +44,7 @@ connmark_tg(struct sk_buff *skb, const struct xt_action_param *par)
        u_int32_t newmark;
 
        ct = nf_ct_get(skb, &ctinfo);
-       if (ct == NULL)
+       if (ct == NULL || nf_ct_is_untracked(ct))
                return XT_CONTINUE;