netdev - Re: [PATCH net-next] tcp: take care of SYN_RECV sockets in tcp_v4_send_ack() and tcp_v6_send

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Message-ID: <CAGHK07A3r1FTDPyNFLKq2S9TaT1COKEGF3wpCgjBmY0+TSnnXg@mail.gmail.com>
Date:   Tue, 11 Jun 2019 08:40:24 +1000
From:   Jonathan Maxwell <jmaxwell37@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH net-next] tcp: take care of SYN_RECV sockets in
 tcp_v4_send_ack() and tcp_v6_send_response()

Sounds good Eric. Thanks

On Tue, Jun 11, 2019 at 8:34 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Mon, Jun 10, 2019 at 3:27 PM Jonathan Maxwell <jmaxwell37@...il.com> wrote:
> >
> > Thanks for fixing that Eric.
>
> Hi Jonathan.
>
> There is no bug actually, at least not on sk->sk_mark part.
>
> I will send a simpler patch so that sock_net_uid() correctly fetches
> sk->sk_uid for FASTOPEN socket.
>
> Thanks !
>
>
>
> >
> > On Tue, Jun 11, 2019 at 7:45 AM Eric Dumazet <edumazet@...gle.com> wrote:
> > >
> > > TCP can send ACK packets on behalf of SYN_RECV sockets.
> > >
> > > tcp_v4_send_ack() and tcp_v6_send_response() incorrectly
> > > dereference sk->sk_mark for non TIME_WAIT sockets.
> > >
> > > This field is not defined for SYN_RECV sockets.
> > >
> > > Using sk_to_full_sk() should get back to the listener socket.
> > >
> > > Note that this also provides a socket pointer to sock_net_uid() calls.
> > >
> > > Fixes: 00483690552c ("tcp: Add mark for TIMEWAIT sockets")
> > > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > > Cc: Jon Maxwell <jmaxwell37@...il.com>
> > > ---
> > >  net/ipv4/tcp_ipv4.c | 6 ++++--
> > >  net/ipv6/tcp_ipv6.c | 1 +
> > >  2 files changed, 5 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> > > index f059fbd81a84314ae6fef37f600b0cf28bd2ad30..2bb27d5eae78efdff52a741904d7526a234595d8 100644
> > > --- a/net/ipv4/tcp_ipv4.c
> > > +++ b/net/ipv4/tcp_ipv4.c
> > > @@ -856,12 +856,14 @@ static void tcp_v4_send_ack(const struct sock *sk,
> > >         if (oif)
> > >                 arg.bound_dev_if = oif;
> > >         arg.tos = tos;
> > > -       arg.uid = sock_net_uid(net, sk_fullsock(sk) ? sk : NULL);
> > >         local_bh_disable();
> > >         ctl_sk = this_cpu_read(*net->ipv4.tcp_sk);
> > > -       if (sk)
> > > +       if (sk) {
> > > +               sk = sk_to_full_sk(sk);
> > >                 ctl_sk->sk_mark = (sk->sk_state == TCP_TIME_WAIT) ?
> > >                                    inet_twsk(sk)->tw_mark : sk->sk_mark;
> > > +       }
> > > +       arg.uid = sock_net_uid(net, sk_fullsock(sk) ? sk : NULL);
> > >         ip_send_unicast_reply(ctl_sk,
> > >                               skb, &TCP_SKB_CB(skb)->header.h4.opt,
> > >                               ip_hdr(skb)->saddr, ip_hdr(skb)->daddr,
> > > diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> > > index ad7039137a20f9ad8581d9ca01347c67aa8a8433..ea4dd988bc7f9a90e0d95283e10db5a517a59027 100644
> > > --- a/net/ipv6/tcp_ipv6.c
> > > +++ b/net/ipv6/tcp_ipv6.c
> > > @@ -884,6 +884,7 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
> > >         }
> > >
> > >         if (sk) {
> > > +               sk = sk_to_full_sk(sk);
> > >                 if (sk->sk_state == TCP_TIME_WAIT) {
> > >                         mark = inet_twsk(sk)->tw_mark;
> > >                         /* autoflowlabel relies on buff->hash */
> > > --
> > > 2.22.0.rc2.383.gf4fbbf30c2-goog
> > >