netdev - Re: [PATCH bpf-next 2/3] bpf: allow bpf_{s,g}etsockopt from cgroup bind{4,6} hooks

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Date:   Tue, 17 Nov 2020 20:05:09 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Stanislav Fomichev <sdf@...gle.com>, Andrey Ignatov <rdna@...com>
Cc:     Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH bpf-next 2/3] bpf: allow bpf_{s,g}etsockopt from cgroup
 bind{4,6} hooks

On Tue, Nov 17, 2020 at 4:17 PM Stanislav Fomichev <sdf@...gle.com> wrote:
>
> I have to now lock/unlock socket for the bind hook execution.
> That shouldn't cause any overhead because the socket is unbound
> and shouldn't receive any traffic.
>
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> ---
>  include/linux/bpf-cgroup.h | 12 ++++++------
>  net/core/filter.c          |  4 ++++
>  net/ipv4/af_inet.c         |  2 +-
>  net/ipv6/af_inet6.c        |  2 +-
>  4 files changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
> index ed71bd1a0825..72e69a0e1e8c 100644
> --- a/include/linux/bpf-cgroup.h
> +++ b/include/linux/bpf-cgroup.h
> @@ -246,11 +246,11 @@ int bpf_percpu_cgroup_storage_update(struct bpf_map *map, void *key,
>         __ret;                                                                 \
>  })
>
> -#define BPF_CGROUP_RUN_PROG_INET4_BIND(sk, uaddr)                             \
> -       BPF_CGROUP_RUN_SA_PROG(sk, uaddr, BPF_CGROUP_INET4_BIND)
> +#define BPF_CGROUP_RUN_PROG_INET4_BIND_LOCK(sk, uaddr)                        \
> +       BPF_CGROUP_RUN_SA_PROG_LOCK(sk, uaddr, BPF_CGROUP_INET4_BIND, NULL)
>
> -#define BPF_CGROUP_RUN_PROG_INET6_BIND(sk, uaddr)                             \
> -       BPF_CGROUP_RUN_SA_PROG(sk, uaddr, BPF_CGROUP_INET6_BIND)
> +#define BPF_CGROUP_RUN_PROG_INET6_BIND_LOCK(sk, uaddr)                        \
> +       BPF_CGROUP_RUN_SA_PROG_LOCK(sk, uaddr, BPF_CGROUP_INET6_BIND, NULL)
>
>  #define BPF_CGROUP_PRE_CONNECT_ENABLED(sk) (cgroup_bpf_enabled && \
>                                             sk->sk_prot->pre_connect)
> @@ -434,8 +434,8 @@ static inline int bpf_percpu_cgroup_storage_update(struct bpf_map *map,
>  #define BPF_CGROUP_RUN_PROG_INET_EGRESS(sk,skb) ({ 0; })
>  #define BPF_CGROUP_RUN_PROG_INET_SOCK(sk) ({ 0; })
>  #define BPF_CGROUP_RUN_PROG_INET_SOCK_RELEASE(sk) ({ 0; })
> -#define BPF_CGROUP_RUN_PROG_INET4_BIND(sk, uaddr) ({ 0; })
> -#define BPF_CGROUP_RUN_PROG_INET6_BIND(sk, uaddr) ({ 0; })
> +#define BPF_CGROUP_RUN_PROG_INET4_BIND_LOCK(sk, uaddr) ({ 0; })
> +#define BPF_CGROUP_RUN_PROG_INET6_BIND_LOCK(sk, uaddr) ({ 0; })
>  #define BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk) ({ 0; })
>  #define BPF_CGROUP_RUN_PROG_INET6_POST_BIND(sk) ({ 0; })
>  #define BPF_CGROUP_RUN_PROG_INET4_CONNECT(sk, uaddr) ({ 0; })
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 2ca5eecebacf..21d91dcf0260 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -6995,6 +6995,8 @@ sock_addr_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>                 return &bpf_sk_storage_delete_proto;
>         case BPF_FUNC_setsockopt:
>                 switch (prog->expected_attach_type) {
> +               case BPF_CGROUP_INET4_BIND:
> +               case BPF_CGROUP_INET6_BIND:
>                 case BPF_CGROUP_INET4_CONNECT:
>                 case BPF_CGROUP_INET6_CONNECT:
>                         return &bpf_sock_addr_setsockopt_proto;
> @@ -7003,6 +7005,8 @@ sock_addr_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>                 }
>         case BPF_FUNC_getsockopt:
>                 switch (prog->expected_attach_type) {
> +               case BPF_CGROUP_INET4_BIND:
> +               case BPF_CGROUP_INET6_BIND:
>                 case BPF_CGROUP_INET4_CONNECT:
>                 case BPF_CGROUP_INET6_CONNECT:
>                         return &bpf_sock_addr_getsockopt_proto;
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index b7260c8cef2e..b94fa8eb831b 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -450,7 +450,7 @@ int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
>         /* BPF prog is run before any checks are done so that if the prog
>          * changes context in a wrong way it will be caught.
>          */
> -       err = BPF_CGROUP_RUN_PROG_INET4_BIND(sk, uaddr);
> +       err = BPF_CGROUP_RUN_PROG_INET4_BIND_LOCK(sk, uaddr);

I think it is ok, but I need to go through the locking paths more.
Andrey,
please take a look as well.

>         if (err)
>                 return err;
>
> diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
> index e648fbebb167..a7e3d170af51 100644
> --- a/net/ipv6/af_inet6.c
> +++ b/net/ipv6/af_inet6.c
> @@ -451,7 +451,7 @@ int inet6_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
>         /* BPF prog is run before any checks are done so that if the prog
>          * changes context in a wrong way it will be caught.
>          */
> -       err = BPF_CGROUP_RUN_PROG_INET6_BIND(sk, uaddr);
> +       err = BPF_CGROUP_RUN_PROG_INET6_BIND_LOCK(sk, uaddr);
>         if (err)
>                 return err;
>
> --
> 2.29.2.299.gdc1121823c-goog
>