linux-kernel - Re: [PATCH] tracing: fix va_list breakage in trace_check

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Date:   Thu, 18 Nov 2021 09:30:32 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Nikita Yushchenko <nikita.yushchenko@...tuozzo.com>
Cc:     Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        kernel@...nvz.org
Subject: Re: [PATCH] tracing: fix va_list breakage in trace_check_vprintf()

On Thu, 18 Nov 2021 07:57:33 +0300
Nikita Yushchenko <nikita.yushchenko@...tuozzo.com> wrote:

> What I don't like here is - trace_check_vprintf() will still extract wrong positional arguments, and use 
> the result as part of it's logic.
> 
> Although with your change such use becomes a no-op, this is unintuitive and can turn easily into real 
> problems with future changes.

That trace_check_vprintf() is just full of unintuitive logic ;-)

Which is why I prefer to keep any remnants of that code in that code and
not spread it around. 

> 
> And, the above comment is inexact...  why we can't test? We can, testing code does no depend on 
> iter->seq. What we can't is - reliably extract str to test.
> 
> If testing seq->full condition is preferred over forcibly consuming args from va_list, then such a test 
> shall be done before trace_check_vprintf() tries to use va_arg(). Will submit a patch doing that.

I'm happy with that patch, but can you please resend it as a top level
patch and not a reply, otherwise my patchwork doesn't catch it and my
scripts will not work on it.

Thanks,

-- Steve