linux-kernel - Re: [PATCH] vsprintf: avoid misleading "(null)" for %px

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Message-ID: <20180205201901.GR29988@eros>
Date:   Tue, 6 Feb 2018 07:19:01 +1100
From:   "Tobin C. Harding" <me@...in.cc>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Adam Borowski <kilobyte@...band.pl>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joe Perches <joe@...ches.com>,
        Kees Cook <keescook@...omium.org>,
        "Roberts, William C" <william.c.roberts@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        David Laight <David.Laight@...LAB.COM>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH] vsprintf: avoid misleading "(null)" for %px

On Mon, Feb 05, 2018 at 09:36:03AM -0800, Randy Dunlap wrote:
> On 02/05/2018 08:49 AM, Steven Rostedt wrote:
> > On Mon, 5 Feb 2018 16:22:19 +0100
> > Adam Borowski <kilobyte@...band.pl> wrote:
> > 
> >> My change touches %px only, where your concern doesn't apply.
> >>
> >> You're right, though, when it comes to %pK:
> >>     printk("%%pK: %pK, %%px: %px\n", 0, 0);
> >> says
> >>     %pK: 00000000ba8bdc0a, %px: 0000000000000000
> >>
> >> So what should we do?  Avoid hashing 0?  Print a special value?
> > 
> > My personal opinion is that NULL should stay NULL and not be hashed.
> > What security issue could be leaked by a NULL? I'm not a security
> > person, that's a real question.
> 
> Agree.

While these views seem valid I don't think we are going to get much
love trying to change %pK to give a smidgen more information when %pK is
arguably out of favour :)

	Tobin