linux-kernel - Re: [kernel-hardening] Re: [PATCH v2] printk: hash addresses printed with %p

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Message-ID: <20171018152858.fe6svcxycvzzadpy@thunk.org>
Date:   Wed, 18 Oct 2017 11:28:58 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     "Tobin C. Harding" <me@...in.cc>
Cc:     Kees Cook <keescook@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        Linus Torvalds <torvalds@...ux-foundation.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 <will.deacon@....com>,
        Chris Fries <cfries@...gle.com>,
        Dave Weinstein <olorin@...gle.com>,
        Daniel Micay <danielmicay@...il.com>,
        Djalal Harouni <tixxdz@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [kernel-hardening] Re: [PATCH v2] printk: hash addresses printed
 with %p

On Wed, Oct 18, 2017 at 01:28:05PM +1100, Tobin C. Harding wrote:
> > >> Does %p[FfSs] leak addresses? Well, I guess it does if they are not
> > >> found in kallsyms, but otherwise you have:
> > >>
> > >>   function+0x<offset>
> > >
> > 
> > They haven't traditionally been a big deal. If they turn out to be
> > problematic, we can deal with it then, IMO.

If it's not in kallsyms, the raw address is probably not going to be
terribly useful --- so even if it's not traditionally been a big deal,
why not just hash them if it's not going to be printed as "function+0x<offset>"?

If nothing else, it will help correlate the random address with other
places where it was printed via %p.

					- Ted