linux-kernel - Re: [PATCH] lib/vsprintf: make-printk-non-secret printks all addresses as unhashed

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Date:   Tue, 2 Feb 2021 17:34:36 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Timur Tabi <timur@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>, Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        willy@...radead.org, akpm@...ux-foundation.org,
        torvalds@...ux-foundation.org, roman.fietze@...na.com,
        john.ogness@...utronix.de, akinobu.mita@...il.com
Subject: Re: [PATCH] lib/vsprintf: make-printk-non-secret printks all
 addresses as unhashed

On Tue, 2 Feb 2021 16:19:20 -0600
Timur Tabi <timur@...nel.org> wrote:

> On 2/2/21 3:52 PM, Kees Cook wrote:
> >> A large warning message is displayed if this option is enabled,
> >> because unhashed addresses, while useful for debugging, exposes
> >> kernel addresses which can be a security risk.  
> 
> > Linus has expressly said "no" to things like this in the past:
> > https://lore.kernel.org/lkml/CA+55aFwieC1-nAs+NFq9RTwaR8ef9hWa4MjNBWL41F-8wM49eA@mail.gmail.com/  
> Maybe I misunderstood, but I thought this is what Vlastimil, Petr, 
> Sergey, John, and Steven asked for.

Maybe Linus changed his mind since then?


  "I also suspect that everybody has already accepted that KASLR isn't
   really working locally anyway (due to all the hw leak models with
   cache and TLB timing), so anybody who can look at kernel messages
   already probably could figure most of those things out."

 https://lore.kernel.org/r/CAHk-=wjnEV2E6vCRxv5S5m27iOjHeVWNbfK=JV8qxot4Do-FgA@mail.gmail.com


-- Steve