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

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Message-ID: <20180205114952.6af99dff@gandalf.local.home>
Date:   Mon, 5 Feb 2018 11:49:52 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Adam Borowski <kilobyte@...band.pl>
Cc:     "Tobin C. Harding" <me@...in.cc>, 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>,
        Randy Dunlap <rdunlap@...radead.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH] vsprintf: avoid misleading "(null)" for %px

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.

-- Steve