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

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Message-ID: <20190221093625.56afccd2@gandalf.local.home>
Date:   Thu, 21 Feb 2019 09:36:25 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Masami Hiramatsu <mhiramat@...nel.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 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.

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?

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

Agreed.

Thanks,

-- Steve