[PATCH 4.19 15/45] ip6_gre: reload ipv6h in prepare_ip6gre_xmit_ipv6

[Greg Kroah-Hartman]

From: Haishuang Yan <yanhaishuang@xxxxxxxxxxxxxxxxxxxx>

[ Upstream commit 3bc817d665ac6d9de89f59df522ad86f5b5dfc03 ]

Since ip6_tnl_parse_tlv_enc_lim() can call pskb_may_pull()
which may change skb->data, so we need to re-load ipv6h at
the right place.

Fixes: 898b29798e36 ("ip6_gre: Refactor ip6gre xmit codes")
Cc: William Tu <u9012063@xxxxxxxxx>
Signed-off-by: Haishuang Yan <yanhaishuang@xxxxxxxxxxxxxxxxxxxx>
Acked-by: William Tu <u9012063@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ipv6/ip6_gre.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -680,12 +680,13 @@ static int prepare_ip6gre_xmit_ipv6(stru
 				    struct flowi6 *fl6, __u8 *dsfield,
 				    int *encap_limit)
 {
-	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
+	struct ipv6hdr *ipv6h;
 	struct ip6_tnl *t = netdev_priv(dev);
 	__u16 offset;
 
 	offset = ip6_tnl_parse_tlv_enc_lim(skb, skb_network_header(skb));
 	/* ip6_tnl_parse_tlv_enc_lim() might have reallocated skb->head */
+	ipv6h = ipv6_hdr(skb);
 
 	if (offset > 0) {
 		struct ipv6_tlv_tnl_enc_lim *tel;