netdev - Re: [PATCH bpf-next v8 04/12] bpf: Only reply field should be writeable

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Message-ID: <CAK6E8=fQzbTu3Y-gNcSc4jQykNO-oDOnQbKtTwsbQh0Lp6BrjQ@mail.gmail.com>
Date:   Wed, 24 Jan 2018 11:58:28 -0800
From:   Yuchung Cheng <ycheng@...gle.com>
To:     Lawrence Brakmo <brakmo@...com>
Cc:     netdev <netdev@...r.kernel.org>, Kernel Team <kernel-team@...com>,
        Blake Matheny <bmatheny@...com>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Neal Cardwell <ncardwell@...gle.com>
Subject: Re: [PATCH bpf-next v8 04/12] bpf: Only reply field should be writeable

On Tue, Jan 23, 2018 at 11:57 PM, Lawrence Brakmo <brakmo@...com> wrote:
> Currently, a sock_ops BPF program can write the op field and all the
> reply fields (reply and replylong). This is a bug. The op field should
> not have been writeable and there is currently no way to use replylong
> field for indices >= 1. This patch enforces that only the reply field
> (which equals replylong[0]) is writeable.
Would this patch be more suitable for -net ?

>
> Fixes: 40304b2a1567 ("bpf: BPF support for sock_ops")
> Signed-off-by: Lawrence Brakmo <brakmo@...com>
Acked-by: Yuchung Cheng <ycheng@...gle.com>

> ---
>  net/core/filter.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 0cf170f..c356ec0 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -3845,8 +3845,7 @@ static bool sock_ops_is_valid_access(int off, int size,
>  {
>         if (type == BPF_WRITE) {
>                 switch (off) {
> -               case offsetof(struct bpf_sock_ops, op) ...
> -                    offsetof(struct bpf_sock_ops, replylong[3]):
> +               case offsetof(struct bpf_sock_ops, reply):
>                         break;
>                 default:
>                         return false;
> --
> 2.9.5
>