[PATCH 22/50] l2tp: Fix PPP header erasure and memory leak

[Luis Henriques]

3.5.7.16 -stable review patch.  If anyone has any objections, please let me know.

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

From: Guillaume Nault <g.nault at alphalink.fr>

commit 55b92b7a11690bc377b5d373872a6b650ae88e64 upstream.

Copy user data after PPP framing header. This prevents erasure of the
added PPP header and avoids leaking two bytes of uninitialised memory
at the end of skb's data buffer.

Signed-off-by: Guillaume Nault <g.nault at alphalink.fr>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/l2tp/l2tp_ppp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 46c7cc7..42dfd0e 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -345,12 +345,12 @@ static int pppol2tp_sendmsg(struct kiocb *iocb, struct socket *sock, struct msgh
 	skb_put(skb, 2);
 
 	/* Copy user data into skb */
-	error = memcpy_fromiovec(skb->data, m->msg_iov, total_len);
+	error = memcpy_fromiovec(skb_put(skb, total_len), m->msg_iov,
+				 total_len);
 	if (error < 0) {
 		kfree_skb(skb);
 		goto error_put_sess_tun;
 	}
-	skb_put(skb, total_len);
 
 	l2tp_xmit_skb(session, skb, session->hdr_len);
 
-- 
1.8.1.2