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

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Message-ID: <CAKH8qBuAoobsVP2Q5KN06fZ2NM3_aMwT7Y2OoKwS4Cf=cv3ZGg@mail.gmail.com>
Date:   Wed, 10 May 2023 14:31:24 -0700
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Alexander 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 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?

> +                    !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
>