netdev - Re: [PATCH net-next] net: core: add SOL_SOCKET filter for bpf getsockopt hook

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Date: Wed, 10 May 2023 23:40:45 +0200
From: Aleksandr Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
To: Stanislav Fomichev <sdf@...gle.com>
Cc: davem@...emloft.net, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Christian Brauner <brauner@...nel.org>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Kuniyuki Iwashima <kuniyu@...zon.com>, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
	bpf@...r.kernel.org
Subject: Re: [PATCH net-next] net: core: add SOL_SOCKET filter for bpf
 getsockopt hook

On Wed, May 10, 2023 at 11:31 PM Stanislav Fomichev <sdf@...gle.com> wrote:
>
> On Wed, May 10, 2023 at 8:23 AM Alexander Mikhalitsyn
> <aleksandr.mikhalitsyn@...onical.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_PIDFD interface:
> > https://lore.kernel.org/all/20230413133355.350571-3-aleksandr.mikhalitsyn@canonical.com/
> >
> > Cc: Alexei Starovoitov <ast@...nel.org>
> > Cc: Daniel Borkmann <daniel@...earbox.net>
> > Cc: Christian Brauner <brauner@...nel.org>
> > Cc: Stanislav Fomichev <sdf@...gle.com>
> > Cc: "David S. Miller" <davem@...emloft.net>
> > Cc: Eric Dumazet <edumazet@...gle.com>
> > Cc: Jakub Kicinski <kuba@...nel.org>
> > Cc: Paolo Abeni <pabeni@...hat.com>
> > Cc: Kuniyuki Iwashima <kuniyu@...zon.com>
> > Cc: linux-kernel@...r.kernel.org
> > Cc: netdev@...r.kernel.org
> > Cc: bpf@...r.kernel.org
> > Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.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(struct sock *sk,
> >         int __ret = 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_bypass_getsockopt, \
> > +               if (((level != 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.

Kind regards,
Alex

>
> > +                    !INDIRECT_CALL_INET_1((sock)->sk_prot->bpf_bypass_getsockopt, \
> >                                         tcp_bpf_bypass_getsockopt,             \
> > -                                       level, optname))                       \
> > +                                       level, optname)))                      \
> >                         __ret = __cgroup_bpf_run_filter_getsockopt(            \
> >                                 sock, level, optname, optval, optlen,          \
> >                                 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 long 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
> >