linux-kernel - Re: [PATCH 1/2 v2] kprobe: Do not use uaccess functions to access kernel memory that can fault

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Date:   Fri, 22 Feb 2019 00:58:12 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        stable@...r.kernel.org, Changbin Du <changbin.du@...il.com>
Subject: Re: [PATCH 1/2 v2] kprobe: Do not use uaccess functions to access
 kernel memory that can fault

On Thu, 21 Feb 2019 09:36:25 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Thu, 21 Feb 2019 16:52:52 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
> > Basically OK to me.
> > Could you use probe_kernel_read() in this context, since probe_mem_read() is a
> > wrapper function for template code.
> > 
> > With that change,
> > 
> > Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
> 
> This already hit Linus's tree. I was able to reproduce the crash, so I
> streamlined it. I should have still pushed more for your ack first.
> Sorry about that.

Oh, never mind. That seems urgent issue for kprobe event.
Thank you very much for fixing it!

> For some reason, I thought the change was in the generic probe code,
> and accepted the probe_mem_read(). Anyway, did you want to send a patch
> to change it to probe_kernel_read(), for the merge window?

No problem.

> > And for the long term, I need to find more efficient (or smarter) way to do it,
> > like strnlen_user() does.
> 
> Agreed.

Thank you,


-- 
Masami Hiramatsu <mhiramat@...nel.org>