[PATCH 3.16 212/217] ipv6: l2tp: fix a potential issue in l2tp_ip6_recv

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From	Ben Hutchings <ben@decadent.org.uk>
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Subject	[PATCH 3.16 212/217] ipv6: l2tp: fix a potential issue in l2tp_ip6_recv
Date	Wed, 27 Apr 2016 02:20:01 +0200
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3.16.35-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>

[ Upstream commit be447f305494e019dfc37ea4cdf3b0e4200b4eba ]

pskb_may_pull() can change skb->data, so we have to load ptr/optr at the
right place.

Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 net/l2tp/l2tp_ip6.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -135,12 +135,11 @@ static int l2tp_ip6_recv(struct sk_buff
 	struct l2tp_tunnel *tunnel = NULL;
 	int length;
 
-	/* Point to L2TP header */
-	optr = ptr = skb->data;
-
 	if (!pskb_may_pull(skb, 4))
 		goto discard;
 
+	/* Point to L2TP header */
+	optr = ptr = skb->data;
 	session_id = ntohl(*((__be32 *) ptr));
 	ptr += 4;
 
@@ -168,6 +167,9 @@ static int l2tp_ip6_recv(struct sk_buff
 		if (!pskb_may_pull(skb, length))
 			goto discard;
 
+		/* Point to L2TP header */
+		optr = ptr = skb->data;
+		ptr += 4;
 		pr_debug("%s: ip recv\n", tunnel->name);
 		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, ptr, length);
 	}

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[PATCH 3.16 212/217] ipv6: l2tp: fix a potential issue in  l2tp_ip6_recv Ben Hutchings <ben@decadent.org.uk> - 2016-04-27 02:20 +0200

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