linux-kernel - Re: [PATCH] libbpf: Remove kprobe_event on failed kprobe_open

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Date:   Mon, 20 Jun 2022 14:51:11 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     chuang <nashuiliang@...il.com>, Jiri Olsa <olsajiri@...il.com>
Cc:     John Fastabend <john.fastabend@...il.com>,
        Jingren Zhou <zhoujingren@...iglobal.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH] libbpf: Remove kprobe_event on failed kprobe_open_legacy

On 6/19/22 3:56 AM, chuang wrote:
> On Sun, Jun 19, 2022 at 5:17 AM Jiri Olsa <olsajiri@...il.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