netdev - Re: [PATCH] bpf: Fix off-by-one in tail call count limiting

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Date:   Thu, 29 Jul 2021 23:37:51 +0200
From:   Johan Almbladh <johan.almbladh@...finetworks.com>
To:     Yonghong Song <yhs@...com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Tony Ambardar <Tony.Ambardar@...il.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH] bpf: Fix off-by-one in tail call count limiting

On Wed, Jul 28, 2021 at 9:13 PM Yonghong Song <yhs@...com> wrote:
> I also checked arm/arm64 jit. I saw the following comments:
>
>          /* if (tail_call_cnt > MAX_TAIL_CALL_CNT)
>           *      goto out;
>           * tail_call_cnt++;
>           */
>
> Maybe we have this MAX_TAIL_CALL_CNT + 1 issue
> for arm/arm64 jit?

That wouldn't be unreasonable. I don't have an arm or arm64 setup
available right now, but I can try to test it in qemu.