From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH net,stable 1/2] l2tp: Fix PPP header erasure and memory leak Date: Wed, 12 Jun 2013 07:50:48 -0700 Message-ID: <1371048648.3252.62.camel@edumazet-glaptop> References: <20130612140723.GB3500@alphalink.fr> <1371048080.3252.61.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, James Chapman , David Miller To: Guillaume Nault Return-path: Received: from mail-ea0-f173.google.com ([209.85.215.173]:48291 "EHLO mail-ea0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753746Ab3FLOuw (ORCPT ); Wed, 12 Jun 2013 10:50:52 -0400 Received: by mail-ea0-f173.google.com with SMTP id g15so6905700eak.18 for ; Wed, 12 Jun 2013 07:50:51 -0700 (PDT) In-Reply-To: <1371048080.3252.61.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 2013-06-12 at 07:41 -0700, Eric Dumazet wrote: > On Wed, 2013-06-12 at 16:07 +0200, Guillaume Nault wrote: > > 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 > > --- > > 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 637a341..681c626 100644 > > --- a/net/l2tp/l2tp_ppp.c > > +++ b/net/l2tp/l2tp_ppp.c > > @@ -346,12 +346,12 @@ 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); > > > > I see no real change in your patch. > > skb_put(skb, X) returns skb->data before the put operation. > > Could you elaborate ? Oh well, I missed the prior skb_put(skb, 2), nevermind