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Message-ID: <1371048648.3252.62.camel@edumazet-glaptop>
Date: Wed, 12 Jun 2013 07:50:48 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: Guillaume Nault <g.nault@...halink.fr>
Cc: netdev@...r.kernel.org, James Chapman <jchapman@...alix.com>,
David Miller <davem@...emloft.net>
Subject: Re: [PATCH net,stable 1/2] l2tp: Fix PPP header erasure and memory
leak
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 <g.nault@...halink.fr>
> > ---
> > 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
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