4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ Upstream commit 21b995a9cb093fff33ec91d7cb3822b882a90a1e ]
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 <edumazet@xxxxxxxxxx>
Cc: Dmitry Kozlov <xeb@xxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv6/ip6_gre.c | 3 +++
net/ipv6/ip6_tunnel.c | 2 ++
2 files changed, 5 insertions(+)
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -582,6 +582,9 @@ static inline int ip6gre_xmit_ipv6(struc
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];
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1313,6 +1313,8 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, str
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;