linux-kernel - Re: [PATCH 0/2] tracing: Detect unsafe dereferencing of pointers from trace events

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Date:   Fri, 26 Feb 2021 20:04:28 -0800
From:   Joe Perches <joe@...ches.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jacob Wen <jian.w.wen@...cle.com>
Subject: Re: [PATCH 0/2] tracing: Detect unsafe dereferencing of pointers
 from trace events

On Fri, 2021-02-26 at 18:33 -0500, Steven Rostedt wrote:
> On Fri, 26 Feb 2021 14:21:00 -0800
> Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 
> > > The second patch handles strings "%s" [..]  
> > 
> > Doing this at runtime really feels like the wrong thing to do.
> > 
> > It won't even protect us from what happened - people like me and
> > Andrew won't even run those tracepoints in the first place, so we
> > won't notice.
> > 
> > It really would be much better in every respect to have this done by
> > checkpatch, I think.
> 
> They are not mutually exclusive. We could have both. One thing that's nice
> about this patch is that it removes the possibility of a real bug. That is,
> it will catch the dereferencing of a string that is not valid, WARN about
> it, but it wont try to dereference it (outside of the
> strcpy_from_kernel_nofault()). And hopefully the warning and lack of data
> they want, will have this get caught during development.
> 
> Also, there's cases that %s is allowed to reference data that I don't know
> if checkpatch would be able to differentiate.

It's not obvious to me how to do that.