l2tp: Fix PPP header erasure and memory leak

[ Upstream commit 55b92b7a11690bc377b5d373872a6b650ae88e64 ]

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@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 9728a7564a703e207714f2c64aca2b70954f8b2e..06bb5b343d54e2c2187bcd6519a1773b7c27ad34 100644 (file)
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -350,12 +350,12 @@ 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);