netdev - Re: [PATCH] sit: reload iphdr in ipip6

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Date:   Tue, 06 Jun 2017 11:35:13 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     yanhaishuang@...s.chinamobile.com
Cc:     eric.dumazet@...il.com, jesse@...nel.org, kuznet@....inr.ac.ru,
        jmorris@...ei.org, yoshfuji@...ux-ipv6.org, kaber@...sh.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sit: reload iphdr in ipip6_rcv

From: 严海双 <yanhaishuang@...s.chinamobile.com>
Date: Tue, 6 Jun 2017 10:09:45 +0800

> 
>> On 5 Jun 2017, at 9:03 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> 
>> On Sun, 2017-06-04 at 14:43 +0800, Haishuang Yan wrote:
>>> Since iptunnel_pull_header() can call pskb_may_pull(),
>>> we must reload any pointer that was related to skb->head.
>>> 
>>> Fixes: a09a4c8dd1ec ("tunnels: Remove encapsulation offloads on decap")
>>> Signed-off-by: Haishuang Yan <yanhaishuang@...s.chinamobile.com>
>>> ---
>>> net/ipv6/sit.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>> 
>>> diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
>>> index 61e5902..af832e7 100644
>>> --- a/net/ipv6/sit.c
>>> +++ b/net/ipv6/sit.c
>>> @@ -657,6 +657,7 @@ static int ipip6_rcv(struct sk_buff *skb)
>>> 		if (iptunnel_pull_header(skb, 0, htons(ETH_P_IPV6),
>>> 		    !net_eq(tunnel->net, dev_net(tunnel->dev))))
>>> 			goto out;
>>> +		iph = ip_hdr(skb);
>>> 
>>> 		err = IP_ECN_decapsulate(iph, skb);
>>> 		if (unlikely(err)) {
>> 
>> This seems unnecessary.
>> 
>> By the time ipip6_rcv() is called, we already have the guarantee the
>> IPv4 header is in skb linear part.
>> 
>> Otherwise we could not use iph->saddr and iph->daddr in the call to
>> ipip6_tunnel_lookup()
>> 
>> Therefore, the pskb_may_pull() is a nop in this particular case.
> 
> Yes, it’s right. Thanks!

Ok, I reverted, thanks everyone.