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Message-ID: <CAKH8qBvp3iNPHrus3NpgwN1JCkSxzTTi3G3WoAR2LKwX1-QzhQ@mail.gmail.com>
Date: Wed, 10 May 2023 14:58:04 -0700
From: Stanislav Fomichev <sdf@...gle.com>
To: Aleksandr Mikhalitsyn <aleksandr.mikhalitsyn@...onical.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 2:41 PM Aleksandr Mikhalitsyn
<aleksandr.mikhalitsyn@...onical.com> wrote:
>
> 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.
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.
> 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
> > >
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