From: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Date: Sun, 3 Apr 2016 14:09:24 +0000 (+0800)
Subject: ipv6: l2tp: fix a potential issue in l2tp_ip6_recv
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=0ad91c67ea1655b3a382c4e9e9e8857053901a48;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git

ipv6: l2tp: fix a potential issue in l2tp_ip6_recv

commit be447f305494e019dfc37ea4cdf3b0e4200b4eba upstream.

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: Willy Tarreau <w@1wt.eu>
---

diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
index e6e8408c9e36..db96af978da5 100644
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -135,12 +135,11 @@ static int l2tp_ip6_recv(struct sk_buff *skb)
 	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 *skb)
 		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);
 	}