[PATCH] ip6_gre: fix a pontential issue in ip6erspan_rcv

[Haishuang Yan]

pskb_may_pull() can change skb->data, so we need to load ipv6h/ershdr at
the right place.

Fixes: 5a963eb61b7c ("ip6_gre: Add ERSPAN native tunnel support")
Cc: William Tu <u9012...@gmail.com>
Signed-off-by: Haishuang Yan <yanhaishu...@cmss.chinamobile.com>
---
 net/ipv6/ip6_gre.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 68e7eef..eab4b56 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -506,12 +506,12 @@ static int ip6erspan_rcv(struct sk_buff *skb, int 
gre_hdr_len,
        struct ip6_tnl *tunnel;
        __be32 index;
 
-       ipv6h = ipv6_hdr(skb);
-       ershdr = (struct erspanhdr *)skb->data;
-
        if (unlikely(!pskb_may_pull(skb, sizeof(*ershdr))))
                return PACKET_REJECT;
 
+       ipv6h = ipv6_hdr(skb);
+       ershdr = (struct erspanhdr *)skb->data;
+
        tpi->key = cpu_to_be32(ntohs(ershdr->session_id) & ID_MASK);
        index = ershdr->md.index;
 
-- 
1.8.3.1