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From:   Aleksandr Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Date:   Thu, 11 May 2023 08:36:18 +0200
Message-ID: <CAEivzxfso6dJCB31MsrCkMg4DXBszY9QxQKsX-x0oMoaUQz5Fg@mail.gmail.com>
Subject: Re: [PATCH net-next] net: core: add SOL_SOCKET filter for bpf
 getsockopt hook
To:     Stanislav Fomichev <sdf@google.com>
Cc:     davem@davemloft.net, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Christian Brauner <brauner@kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Kuniyuki Iwashima <kuniyu@amazon.com>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        bpf@vger.kernel.org
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On Wed, May 10, 2023 at 11:58=E2=80=AFPM Stanislav Fomichev <sdf@google.com=
> wrote:
>
> On Wed, May 10, 2023 at 2:41=E2=80=AFPM Aleksandr Mikhalitsyn
> <aleksandr.mikhalitsyn@canonical.com> wrote:
> >
> > On Wed, May 10, 2023 at 11:31=E2=80=AFPM Stanislav Fomichev <sdf@google=
.com> wrote:
> > >
> > > On Wed, May 10, 2023 at 8:23=E2=80=AFAM Alexander Mikhalitsyn
> > > <aleksandr.mikhalitsyn@canonical.com> wrote:
> > > >
> > > > We have per struct proto ->bpf_bypass_getsockopt callback
> > > > to filter out bpf socket cgroup getsockopt hook from being called.
> > > >
> > > > It seems worthwhile to add analogical helper for SOL_SOCKET
> > > > level socket options. First user will be SO_PEERPIDFD.
> > > >
> > > > This patch was born as a result of discussion around a new SCM_PIDF=
D interface:
> > > > https://lore.kernel.org/all/20230413133355.350571-3-aleksandr.mikha=
litsyn@canonical.com/
> > > >
> > > > Cc: Alexei Starovoitov <ast@kernel.org>
> > > > Cc: Daniel Borkmann <daniel@iogearbox.net>
> > > > Cc: Christian Brauner <brauner@kernel.org>
> > > > Cc: Stanislav Fomichev <sdf@google.com>
> > > > Cc: "David S. Miller" <davem@davemloft.net>
> > > > Cc: Eric Dumazet <edumazet@google.com>
> > > > Cc: Jakub Kicinski <kuba@kernel.org>
> > > > Cc: Paolo Abeni <pabeni@redhat.com>
> > > > Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
> > > > Cc: linux-kernel@vger.kernel.org
> > > > Cc: netdev@vger.kernel.org
> > > > Cc: bpf@vger.kernel.org
> > > > Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonic=
al.com>
> > > > ---
> > > >  include/linux/bpf-cgroup.h | 8 +++++---
> > > >  include/net/sock.h         | 1 +
> > > >  net/core/sock.c            | 5 +++++
> > > >  3 files changed, 11 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.=
h
> > > > index 57e9e109257e..97d8a49b35bf 100644
> > > > --- a/include/linux/bpf-cgroup.h
> > > > +++ b/include/linux/bpf-cgroup.h
> > > > @@ -387,10 +387,12 @@ static inline bool cgroup_bpf_sock_enabled(st=
ruct sock *sk,
> > > >         int __ret =3D retval;                                      =
              \
> > > >         if (cgroup_bpf_enabled(CGROUP_GETSOCKOPT) &&               =
            \
> > > >             cgroup_bpf_sock_enabled(sock, CGROUP_GETSOCKOPT))      =
            \
> > > > -               if (!(sock)->sk_prot->bpf_bypass_getsockopt ||     =
            \
> > > > -                   !INDIRECT_CALL_INET_1((sock)->sk_prot->bpf_bypa=
ss_getsockopt, \
> > > > +               if (((level !=3D SOL_SOCKET) ||                    =
              \
> > > > +                    !sock_bpf_bypass_getsockopt(level, optname)) &=
&           \
> > > > +                   (!(sock)->sk_prot->bpf_bypass_getsockopt ||    =
            \
> > >
> > > Any reason we are not putting this into bpf_bypass_getsockopt for
> > > af_unix struct proto? SO_PEERPIDFD seems relevant only for af_unix?
> >
> > Yes, that should work perfectly well. The reason why I'm going this
> > way is that we are
> > declaring all SOL_SOCKET-level options in the net/core/sock.c which is
> > not specific to any address family.
> > It seems reasonable to have a way to filter out getsockopt for these
> > options too.
> >
> > But I'm not insisting on that way.
>
> Yeah, let's move it into af_unix struct proto for now. That should
> avoid adding extra conditionals for a few places that care about
> performance (tcp zerocopy fastpath).
> If we'd ever need to filter out generic SOL_SOCKET level options that
> apply for all sockets, we might put (and copy-paste) them in the
> respective {tcp,udp,unix,etc}_bpf_bypass_getsockopt.

Will do.

Thanks!

Kind regards,
Alex

>
> > Kind regards,
> > Alex
> >
> > >
> > > > +                    !INDIRECT_CALL_INET_1((sock)->sk_prot->bpf_byp=
ass_getsockopt, \
> > > >                                         tcp_bpf_bypass_getsockopt, =
            \
> > > > -                                       level, optname))           =
            \
> > > > +                                       level, optname)))          =
            \
> > > >                         __ret =3D __cgroup_bpf_run_filter_getsockop=
t(            \
> > > >                                 sock, level, optname, optval, optle=
n,          \
> > > >                                 max_optlen, retval);               =
            \
> > > > diff --git a/include/net/sock.h b/include/net/sock.h
> > > > index 8b7ed7167243..530d6d22f42d 100644
> > > > --- a/include/net/sock.h
> > > > +++ b/include/net/sock.h
> > > > @@ -1847,6 +1847,7 @@ int sk_getsockopt(struct sock *sk, int level,=
 int optname,
> > > >                   sockptr_t optval, sockptr_t optlen);
> > > >  int sock_getsockopt(struct socket *sock, int level, int op,
> > > >                     char __user *optval, int __user *optlen);
> > > > +bool sock_bpf_bypass_getsockopt(int level, int optname);
> > > >  int sock_gettstamp(struct socket *sock, void __user *userstamp,
> > > >                    bool timeval, bool time32);
> > > >  struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned lon=
g header_len,
> > > > diff --git a/net/core/sock.c b/net/core/sock.c
> > > > index 5440e67bcfe3..194a423eb6e5 100644
> > > > --- a/net/core/sock.c
> > > > +++ b/net/core/sock.c
> > > > @@ -1963,6 +1963,11 @@ int sock_getsockopt(struct socket *sock, int=
 level, int optname,
> > > >                              USER_SOCKPTR(optlen));
> > > >  }
> > > >
> > > > +bool sock_bpf_bypass_getsockopt(int level, int optname)
> > > > +{
> > > > +       return false;
> > > > +}
> > > > +
> > > >  /*
> > > >   * Initialize an sk_lock.
> > > >   *
> > > > --
> > > > 2.34.1
> > > >