[PATCH] sit: reload iphdr in ipip6_rcv

[PATCH] sit: reload iphdr in ipip6_rcv

[Haishuang Yan]

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@cmss.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)) {
-- 
1.8.3.1

Re: [PATCH] sit: reload iphdr in ipip6_rcv

[David Miller]

From: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Date: Sun,  4 Jun 2017 14:43:43 +0800

> 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@cmss.chinamobile.com>

Applied and queued up for -stable, thank you.

Re: [PATCH] sit: reload iphdr in ipip6_rcv

[Eric Dumazet]

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@cmss.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.

Re: [PATCH] sit: reload iphdr in ipip6_rcv

[David Miller]

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

> 
>> On 5 Jun 2017, at 9:03 PM, Eric Dumazet <eric.dumazet@gmail.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@cmss.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.