[PATCH 3.16 255/370] ip6_tunnel: must reload ipv6h in ip6ip6_tnl_xmit()

From	Ben Hutchings <ben@decadent.org.uk>
Newsgroups	linux.kernel
Subject	[PATCH 3.16 255/370] ip6_tunnel: must reload ipv6h in ip6ip6_tnl_xmit()
Date	2017-03-10 15:00 +0100
Message-ID	<tjtfm-4NB-83@gated-at.bofh.it> (permalink)
References	<tjrnb-3sF-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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3.16.42-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@google.com>

commit 21b995a9cb093fff33ec91d7cb3822b882a90a1e upstream.

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@google.com>
Cc: Dmitry Kozlov <xeb@mail.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: adjust context, indentation]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 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
@@ -819,6 +819,9 @@ 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
@@ -1118,6 +1118,8 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, str
 		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];

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[PATCH 3.16 255/370] ip6_tunnel: must reload ipv6h in  ip6ip6_tnl_xmit() Ben Hutchings <ben@decadent.org.uk> - 2017-03-10 15:00 +0100

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