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From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Mon, 20 Mar 2023 08:20:36 -0700
Message-ID: <CAADnVQJXAkyCd0vXPQa54gQgRpvG4Z7N+JD3+HXcbFb-+O=GLA@mail.gmail.com>
Subject: Re: [PATCH v2] kernel: bpf: stackmap: fix a possible sleep-in-atomic
 bug in bpf_mmap_unlock_get_irq_work()
To:     Teng Qi <starmiku1207184332@gmail.com>
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        bpf <bpf@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        baijiaju1990@outlook.com
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On Mon, Mar 20, 2023 at 5:28=E2=80=AFAM Teng Qi <starmiku1207184332@gmail.c=
om> wrote:
>
> Yeah, we got your points. There are two key questions. The first question=
 is
> that preempt_disable() and preempt_enable() will be conflicted with vfree=
()
> before the mmap_read_unlock().

What does this sentence mean?

> The second question is that thousands callers
> of up_read() only make sure irqs_disabled() =3D=3D false needed fixed if
> the mmap_read_unlock() is fixed.

that doesn't answer my question either.

> Detecting ebpf bugs can be challenging since it is difficult to prove tha=
t a
> bug can be triggered during runtime, as well as fixing the bug. We decide=
d to
> give up this patch that fixes the possible sleep-in-atomic bug in
> bpf_mmap_unlock_get_irq_work(). Instead, we will focus on improving our s=
tatic
> analysis tool to find ebpf-specific bugs.

Please don't.