Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 19 Feb 2019 11:18:02 -0500
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Andy Lutomirski <luto@amacapital.net>,
        Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        stable <stable@vger.kernel.org>,
        Changbin Du <changbin.du@gmail.com>,
        Jann Horn <jannh@google.com>,
        Kees Cook <keescook@chromium.org>,
        Andy Lutomirski <luto@kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [PATCH 1/2 v2] kprobe: Do not use uaccess functions to access
 kernel memory that can fault
Message-ID: <20190219111802.1d6dbaa3@gandalf.local.home>
In-Reply-To: <CAHk-=wh9XrOykA5J9RQ7zaBio-S_D+1AE+rGnBYWSd==pCXh+w@mail.gmail.com>
References: <20190215174712.372898450@goodmis.org>
        <20190215174945.557218316@goodmis.org>
        <CAHk-=wjP4bEYCFaKZVG4kLWmYBctyfsW9jjhC91tiTk9WwB8Rg@mail.gmail.com>
        <20190215171539.4682f0b4@gandalf.local.home>
        <300C4516-A093-43AE-8707-1C42486807A4@amacapital.net>
        <20190215191949.04604191@gandalf.local.home>
        <CAHk-=wgJzNp0R3cVhjBPHTR4X9sOvHdqK4UVFfbsOKQ6L=A_eQ@mail.gmail.com>
        <CAHk-=wh9XrOykA5J9RQ7zaBio-S_D+1AE+rGnBYWSd==pCXh+w@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


[ Added Masami too. Start of thread is here:
  http://lkml.kernel.org/r/20190215174712.372898450@goodmis.org ]

On Mon, 18 Feb 2019 10:23:44 -0800
Linus Torvalds <torvalds@linux-foundation.org> wrote:

> So it would be good to not just say "user or kernel", but actually say
> what *kind* of kernel access it expects.

Note, kprobes are a different kind of beast. I've used kprobes to probe
userspace information as well as kernel. Heck, I could see someone
even using kprobes to probe IO memory to check if a device is doing
what they expect it's doing.

Basically, a kprobe is mostly used for debugging what's happening in a
live kernel, to read any address. But for those that are more security
minded, perhaps we could add "layers" via CONFIG or /sys files that
prevent kprobes from doing certain kinds of probes?

-- Steve