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Subject: Re: [PATCH bpf-next v3] bpf: Change value of MAX_TAIL_CALL_CNT from
 32 to 33
To:     Tiezhu Yang <yangtiezhu@loongson.cn>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>
Cc:     netdev@vger.kernel.org, bpf@vger.kernel.org,
        linux-kernel@vger.kernel.org, Xuefeng Li <lixuefeng@loongson.cn>,
        Johan Almbladh <johan.almbladh@anyfinetworks.com>,
        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>, illusionist.neo@gmail.com,
        zlim.lnx@gmail.com, naveen.n.rao@linux.ibm.com,
        luke.r.nels@gmail.com, xi.wang@gmail.com, bjorn@kernel.org,
        iii@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com,
        udknight@gmail.com, davem@davemloft.net
References: <1635508430-2918-1-git-send-email-yangtiezhu@loongson.cn>
From:   Daniel Borkmann <daniel@iogearbox.net>
Message-ID: <f80b4756-8e74-6ee8-c367-30f8d2771bfb@iogearbox.net>
Date:   Mon, 1 Nov 2021 16:44:51 +0100
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On 10/29/21 1:53 PM, Tiezhu Yang wrote:
[...]
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index b6c72af..6d10292 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -1565,7 +1565,8 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
>   
>   		if (unlikely(index >= array->map.max_entries))
>   			goto out;
> -		if (unlikely(tail_call_cnt > MAX_TAIL_CALL_CNT))
> +
> +		if (unlikely(tail_call_cnt == MAX_TAIL_CALL_CNT))
>   			goto out;
>   

Why making it less robust by going with == rather than >= ?