netdev - Re: [PATCH bpf] bpf: tcp: recv() should return 0 when the peer socket is closed

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAADnVQKYHg-ZmzEibZ7TtZdyfNK+r7FQfv_DuJK44LdRuATDGw@mail.gmail.com>
Date:   Fri, 12 Jun 2020 15:13:14 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Jakub Sitnicki <jakub@...udflare.com>
Cc:     Sabrina Dubroca <sd@...asysnail.net>,
        Network Development <netdev@...r.kernel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf] bpf: tcp: recv() should return 0 when the peer socket
 is closed

On Fri, Jun 12, 2020 at 3:18 AM Jakub Sitnicki <jakub@...udflare.com> wrote:
>
> On Wed, 10 Jun 2020 12:19:43 +0200
> Sabrina Dubroca <sd@...asysnail.net> wrote:
>
> > If the peer is closed, we will never get more data, so
> > tcp_bpf_wait_data will get stuck forever. In case we passed
> > MSG_DONTWAIT to recv(), we get EAGAIN but we should actually get
> > 0.
> >
> > From man 2 recv:
> >
> >     RETURN VALUE
> >
> >     When a stream socket peer has performed an orderly shutdown, the
> >     return value will be 0 (the traditional "end-of-file" return).
> >
> > This patch makes tcp_bpf_wait_data always return 1 when the peer
> > socket has been shutdown. Either we have data available, and it would
> > have returned 1 anyway, or there isn't, in which case we'll call
> > tcp_recvmsg which does the right thing in this situation.
> >
> > Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
> > Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
> > ---
> >  net/ipv4/tcp_bpf.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
> > index 2b915aafda42..7aa68f4aae6c 100644
> > --- a/net/ipv4/tcp_bpf.c
> > +++ b/net/ipv4/tcp_bpf.c
> > @@ -245,6 +245,9 @@ static int tcp_bpf_wait_data(struct sock *sk, struct sk_psock *psock,
> >       DEFINE_WAIT_FUNC(wait, woken_wake_function);
> >       int ret = 0;
> >
> > +     if (sk->sk_shutdown & RCV_SHUTDOWN)
> > +             return 1;
> > +
> >       if (!timeo)
> >               return ret;
> >
>
> Acked-by: Jakub Sitnicki <jakub@...udflare.com>

Applied. Thanks