linux-kernel - Re: [PATCH v4] scripts: add leaking

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Date:   Wed, 8 Nov 2017 07:58:20 +1100
From:   "Tobin C. Harding" <me@...in.cc>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Theodore Ts'o <tytso@....edu>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Tycho Andersen <tycho@...ker.com>,
        "Roberts, William C" <william.c.roberts@...el.com>,
        Tejun Heo <tj@...nel.org>,
        Jordan Glover <Golden_Miller83@...tonmail.ch>,
        Greg KH <gregkh@...uxfoundation.org>,
        Petr Mladek <pmladek@...e.com>, Joe Perches <joe@...ches.com>,
        Ian Campbell <ijc@...lion.org.uk>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <wilal.deacon@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Chris Fries <cfries@...gle.com>,
        Dave Weinstein <olorin@...gle.com>,
        Daniel Micay <danielmicay@...il.com>,
        Djalal Harouni <tixxdz@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>
Subject: Re: [PATCH v4] scripts: add leaking_addresses.pl

On Tue, Nov 07, 2017 at 01:56:05PM +0000, David Laight wrote:
> From: Tobin C. Harding
> > Sent: 07 November 2017 10:32
> >
> > Currently we are leaking addresses from the kernel to user space. This
> > script is an attempt to find some of those leakages. Script parses
> > `dmesg` output and /proc and /sys files for hex strings that look like
> > kernel addresses.
> ...
> 
> Maybe the %p that end up in dmesg (via the kernel message buffer) should
> be converted to text in a form that allows the code that reads them to
> substitute alternate text for non-root users?
>
> Then the actual addresses will be available to root (who can probably
> get most by other means) but not to the casual observer.

Interesting idea. Isn't the same outcome already achieved with
dmesg_restrict. I appreciate that this does beg the question 'why are we
scanning dmesg then?'

There has not been much discussion on dmesg_restrict. Is dmesg_restrict
good enough that we needn't bother scanning it?

thanks for your input,
Tobin.