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From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Tue, 30 Mar 2021 16:16:44 -0700
Message-ID: <CAADnVQK+n69_uUm6Ac1WgvqM4X0_74nXHwkYxbkWFc1F5hU98Q@mail.gmail.com>
Subject: Re: [PATCH bpf-next v2] bpf: check flags in 'bpf_ringbuf_discard()'
 and 'bpf_ringbuf_submit()'
To:     Pedro Tammela <pctammela@gmail.com>
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>, Joe Stringer <joe@cilium.io>,
        Quentin Monnet <quentin@isovalent.com>,
        "open list:BPF (Safe dynamic programs and tools)" 
        <netdev@vger.kernel.org>,
        "open list:BPF (Safe dynamic programs and tools)" 
        <bpf@vger.kernel.org>, open list <linux-kernel@vger.kernel.org>,
        Pedro Tammela <pctammela@mojatatu.com>
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On Tue, Mar 30, 2021 at 3:54 PM Pedro Tammela <pctammela@gmail.com> wrote:
>
>  BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags)
>  {
> +       if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP)))
> +               return -EINVAL;
> +
>         bpf_ringbuf_commit(sample, flags, false /* discard */);
> +
>         return 0;

I think ringbuf design was meant for bpf_ringbuf_submit to never fail.
If we do flag validation it probably should be done at the verifier time.