ip6_tunnel: must reload ipv6h in ip6ip6_tnl_xmit()

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: c12b395 ("gre: Support GRE over IPv6") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Dmitry Kozlov <xeb@mail.ru> Signed-off-by: David S. Miller <davem@davemloft.net>
mariux64 · Jan 24, 2017 · 21b995a · 21b995a
1 parent d0fa28f
commit 21b995a
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diff --git 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
@@ -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;