[PATCH v2 net 1/2] ip6_tunnel: must reload ipv6h in ip6ip6_tnl_xmit()

[Eric Dumazet]

Since ip6_tnl_parse_tlv_enc_lim() can call pskb_may_pull(),
we must reload any pointer that was related to skb->head
(or skb->data), or risk use after free.

Fixes: c12b395a4664 ("gre: Support GRE over IPv6")
Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Dmitry Kozlov <x...@mail.ru>
---
 net/ipv6/ip6_gre.c    | 3 +++
 net/ipv6/ip6_tunnel.c | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 
75b6108234dd05a54af0ae51c7c11eaf1ca2..558631860d91bbcb1321a4b566b6e92ddcaf 
100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -582,6 +582,9 @@ static inline int ip6gre_xmit_ipv6(struct sk_buff *skb, 
struct net_device *dev)
                return -1;
 
        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;
                tel = (struct ipv6_tlv_tnl_enc_lim 
*)&skb_network_header(skb)[offset];
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 
753d6d0860fb14c100ab8b20799782ab8160..02923f956ac8ba5f3270e8d5282fd9637c2d 
100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1303,6 +1303,8 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device 
*dev)
                fl6.flowlabel = key->label;
        } else {
                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;
 
-- 
2.11.0.483.g087da7b7c-goog