linux-kernel - Re: [PATCH bpf-next 5/6] bpf: Improve tracing recursion prevention mechanism

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CALOAHbCvZP1-x7Uc39zUFgLdxxvZUVPY9Eh6bL2vjDx_BZSyug@mail.gmail.com>
Date:   Thu, 27 Apr 2023 23:43:35 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        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>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        bpf <bpf@...r.kernel.org>, linux-trace-kernel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next 5/6] bpf: Improve tracing recursion prevention mechanism

On Thu, Apr 27, 2023 at 11:39 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Thu, Apr 27, 2023 at 8:36 AM Steven Rostedt <rostedt@...dmis.org> wrote:
> >
> > On Thu, 27 Apr 2023 23:23:31 +0800
> > Yafang Shao <laoar.shao@...il.com> wrote:
> >
> > > > But I thought you can run a bpf_prog from another bpf_prog. So you don't
> > > > want to prevent it. You need other logic to detect if it was not suppose to
> > > > recurs.
> > > >
> > >
> > > If so, we have to keep the prog->active to prevent it, then I'm not
> > > sure if it is worth adding test_recursion_*().
> >
> > I thought that the whole point of this exercise was because the
> > migrate_disable() itself could be traced (or call something that can), and
> > that's outside of prog->active protection. Which the test_recursion_*()
> > code was created for.
>
> Not sure where did this come from.
> migrate_enable/disable were added to deny list back in 2021.

Hi Alexei,

Don't be uneasy.  It is not good to play word games.
What Steven really meant is the preempt_count_{sub, add}.
Anyway thanks Steven for the help with this exercise.

-- 
Regards
Yafang