[PATCH 3.2 111/115] ipv4: l2tp: fix a potential issue in l2tp_ip_recv
From: Ben Hutchings
Date: Tue Apr 26 2016 - 19:52:16 EST
3.2.80-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Haishuang Yan <yanhaishuang@xxxxxxxxxxxxxxxxxxxx>
[ Upstream commit 5745b8232e942abd5e16e85fa9b27cc21324acf0 ]
pskb_may_pull() can change skb->data, so we have to load ptr/optr at the
right place.
Signed-off-by: Haishuang Yan <yanhaishuang@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
net/l2tp/l2tp_ip.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -129,12 +129,11 @@ static int l2tp_ip_recv(struct sk_buff *
int length;
int offset;
- /* 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;
@@ -162,6 +161,9 @@ static int l2tp_ip_recv(struct sk_buff *
if (!pskb_may_pull(skb, length))
goto discard;
+ /* Point to L2TP header */
+ optr = ptr = skb->data;
+ ptr += 4;
printk(KERN_DEBUG "%s: ip recv: ", tunnel->name);
offset = 0;