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Subject: Re: [PATCH] libbpf: Remove kprobe_event on failed kprobe_open_legacy
To:     chuang <nashuiliang@gmail.com>, Jiri Olsa <olsajiri@gmail.com>
Cc:     John Fastabend <john.fastabend@gmail.com>,
        Jingren Zhou <zhoujingren@didiglobal.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        KP Singh <kpsingh@kernel.org>, netdev@vger.kernel.org,
        bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
        Masami Hiramatsu <mhiramat@kernel.org>
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 <62ad50fa9d42d_24b34208d6@john.notmuch>
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 <CACueBy4Nr+rqJjZ3guBimd6t36V5B3CBp6_oZVMRzLvMZoTRpg@mail.gmail.com>
From:   Daniel Borkmann <daniel@iogearbox.net>
Message-ID: <1b813650-baac-a93e-97b0-11967080fdfe@iogearbox.net>
Date:   Mon, 20 Jun 2022 14:51:11 +0200
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On 6/19/22 3:56 AM, chuang wrote:
> On Sun, Jun 19, 2022 at 5:17 AM Jiri Olsa <olsajiri@gmail.com> wrote:
>>
>> just curious.. is that because of ipmodify flag on ftrace_ops?
>> AFAICS that be a poblem just for kretprobes, cc-ing Masami
> 
> Yes, the core reason is caused by ipmodify flag (not only for kretprobes).
> Before commit 0bc11ed5ab60 ("kprobes: Allow kprobes coexist with
> livepatch"), it's very easy to trigger this problem.
> The kprobe has other problems and is communicating with Masami.
> 
> With this fix, whenever an error is returned after
> add_kprobe_event_legacy(), this guarantees cleanup of the kprobe
> event.

The details from this follow-up conversation should definitely be part of
the commit description, please add them to a v2 as otherwise context is
missing if we look at the commit again in say few months from now. Also,
would be good if Masami could provide ack given 0bc11ed5ab60.

Thanks,
Daniel