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

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Date:   Tue, 17 Oct 2017 20:35:16 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Tobin C. Harding" <me@...in.cc>
Cc:     kernel-hardening@...ts.openwall.com,
        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 <will.deacon@....com>,
        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
Subject: Re: [PATCH v2] printk: hash addresses printed with %p

On Wed, 18 Oct 2017 10:15:59 +1100
"Tobin C. Harding" <me@...in.cc> 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>  
> 
> You are correct %pF and %pS print an offset. Does this provide an attack vector,
> I didn't think so but I'm no security expert. If they do then we need to amend
> those calls also.

Hopefully not. We changed stack dumps to use them only instead of
showing addresses because of the location leak.

-- Steve