linux-kernel - Re: [PATCH v2 1/2] ip_tunnel: fix potential issue in ip_tunnel

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Message-Id: <F11E2C01-13F4-4BDD-8380-92F57DA884F6@cmss.chinamobile.com>
Date:   Thu, 8 Jun 2017 11:07:51 +0800
From:   严海双 <yanhaishuang@...s.chinamobile.com>
To:     Pravin Shelar <pshelar@....org>
Cc:     "=David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Pravin B Shelar <pshelar@...ira.com>
Subject: Re: [PATCH v2 1/2] ip_tunnel: fix potential issue in ip_tunnel_rcv



> On 8 Jun 2017, at 10:13 AM, Pravin Shelar <pshelar@....org> wrote:
> 
> On Wed, Jun 7, 2017 at 5:57 PM, Haishuang Yan
> <yanhaishuang@...s.chinamobile.com> wrote:
>> When ip_tunnel_rcv fails, the tun_dst won't be freed, so move
>> skb_dst_set to begin and tun_dst would be freed by kfree_skb.
>> 
>> CC: Pravin B Shelar <pshelar@...ira.com>
>> Fixes: 2e15ea390e6f ("ip_gre: Add support to collect tunnel metadata.")
>> Signed-off-by: Haishuang Yan <yanhaishuang@...s.chinamobile.com390e>
>> ---
>> net/ipv4/ip_tunnel.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>> 
>> diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
>> index b878ecb..27fc20f 100644
>> --- a/net/ipv4/ip_tunnel.c
>> +++ b/net/ipv4/ip_tunnel.c
>> @@ -386,6 +386,9 @@ int ip_tunnel_rcv(struct ip_tunnel *tunnel, struct sk_buff *skb,
>>        const struct iphdr *iph = ip_hdr(skb);
>>        int err;
>> 
>> +       if (tun_dst)
>> +               skb_dst_set(skb, (struct dst_entry *)tun_dst);
>> +
> If dst is set so early, skb_scrub_packet() would remove the tunnel dst
> reference.
> It is better to call skb_dst_drop() from error code path.

Yes, I will change it in v3 commit, thanks!

> 
>> #ifdef CONFIG_NET_IPGRE_BROADCAST
>>        if (ipv4_is_multicast(iph->daddr)) {
>>                tunnel->dev->stats.multicast++;
>> @@ -439,9 +442,6 @@ int ip_tunnel_rcv(struct ip_tunnel *tunnel, struct sk_buff *skb,
>>                skb->dev = tunnel->dev;
>>        }
>> 
>> -       if (tun_dst)
>> -               skb_dst_set(skb, (struct dst_entry *)tun_dst);
>> -
>>        gro_cells_receive(&tunnel->gro_cells, skb);
>>        return 0;
>> 
>> --
>> 1.8.3.1
>> 
>> 
>> 
>