netdev - Re: [PATCH bpf] libbpf: fix to reject unknown flags in xsk_socket_

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Message-ID: <CAEf4BzYG5VJbvkQC8v6KL=YN7=ywDRVYxsH=L4gE_1PFUeamXA@mail.gmail.com>
Date:   Mon, 11 Mar 2019 09:53:12 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Magnus Karlsson <magnus.karlsson@...el.com>
Cc:     bjorn.topel@...el.com, maciejromanfijalkowski@...il.com,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf] libbpf: fix to reject unknown flags in xsk_socket__create()

On Mon, Mar 11, 2019 at 7:52 AM Magnus Karlsson
<magnus.karlsson@...el.com> wrote:
>
> In xsk_socket__create(), the libbpf_flags field was not checked for
> setting currently unused/unknown flags. This patch fixes that by returning
> -EINVAL if the user has set any flag that is not in use at this point
> in time.
>
> Fixes: 1cad07884239 ("libbpf: add support for using AF_XDP sockets")
> Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
> ---
>  tools/lib/bpf/xsk.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index f98ac82..912f942 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -126,8 +126,8 @@ static void xsk_set_umem_config(struct xsk_umem_config *cfg,
>         cfg->frame_headroom = usr_cfg->frame_headroom;
>  }
>
> -static void xsk_set_xdp_socket_config(struct xsk_socket_config *cfg,
> -                                     const struct xsk_socket_config *usr_cfg)
> +static int xsk_set_xdp_socket_config(struct xsk_socket_config *cfg,
> +                                    const struct xsk_socket_config *usr_cfg)
>  {
>         if (!usr_cfg) {
>                 cfg->rx_size = XSK_RING_CONS__DEFAULT_NUM_DESCS;
> @@ -135,14 +135,19 @@ static void xsk_set_xdp_socket_config(struct xsk_socket_config *cfg,
>                 cfg->libbpf_flags = 0;
>                 cfg->xdp_flags = 0;
>                 cfg->bind_flags = 0;
> -               return;
> +               return 0;
>         }
>
> +       if (cfg->libbpf_flags & ~XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD)
> +               return -EINVAL;
> +

Shouldn't this be checking usr_cfg->libbpf_flags instead?

Also, what about bind_flags and xdp_flags? For those we are deferring
to underlying systems to check extra flags?


>         cfg->rx_size = usr_cfg->rx_size;
>         cfg->tx_size = usr_cfg->tx_size;
>         cfg->libbpf_flags = usr_cfg->libbpf_flags;
>         cfg->xdp_flags = usr_cfg->xdp_flags;
>         cfg->bind_flags = usr_cfg->bind_flags;
> +
> +       return 0;
>  }
>
>  int xsk_umem__create(struct xsk_umem **umem_ptr, void *umem_area, __u64 size,
> @@ -557,7 +562,9 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>         }
>         strncpy(xsk->ifname, ifname, IFNAMSIZ);
>
> -       xsk_set_xdp_socket_config(&xsk->config, usr_config);
> +       err = xsk_set_xdp_socket_config(&xsk->config, usr_config);
> +       if (err)
> +               goto out_socket;
>
>         if (rx) {
>                 err = setsockopt(xsk->fd, SOL_XDP, XDP_RX_RING,
> --
> 2.7.4
>