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

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Message-ID: <20230427113602.0e49c0d1@gandalf.local.home>
Date:   Thu, 27 Apr 2023 11:36:02 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, mhiramat@...nel.org,
        bpf@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next 5/6] bpf: Improve tracing recursion prevention
 mechanism

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.

-- Steve