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

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Message-ID: <CACueBy4Nr+rqJjZ3guBimd6t36V5B3CBp6_oZVMRzLvMZoTRpg@mail.gmail.com>
Date:   Sun, 19 Jun 2022 09:56:03 +0800
From:   chuang <nashuiliang@...il.com>
To:     Jiri Olsa <olsajiri@...il.com>
Cc:     John Fastabend <john.fastabend@...il.com>,
        Jingren Zhou <zhoujingren@...iglobal.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        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

Hi Jiri,

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.