[4.2.y-ckt stable] Patch "ipv6: l2tp: fix a potential issue in l2tp_ip6_recv" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ipv6: l2tp: fix a potential issue in l2tp_ip6_recv

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt9.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From f937d9f3ad19b3e9afb02320d37006f0d6658b33 Mon Sep 17 00:00:00 2001
From: Haishuang Yan <yanhaishuang at cmss.chinamobile.com>
Date: Sun, 3 Apr 2016 22:09:24 +0800
Subject: ipv6: l2tp: fix a potential issue in l2tp_ip6_recv

[ 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 at cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/l2tp/l2tp_ip6.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
index 0ce9da9..36f8fa2 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);
 	}
--
2.7.4