kernel-hardening - Re: [PATCH V8 1/2] printk: remove tabular output for NULL pointer

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Message-ID: <20171026062734.GH12341@eros>
Date: Thu, 26 Oct 2017 17:27:34 +1100
From: "Tobin C. Harding" <me@...in.cc>
To: Joe Perches <joe@...ches.com>
Cc: kernel-hardening@...ts.openwall.com,
	"Jason A. Donenfeld" <Jason@...c4.com>,
	Theodore Ts'o <tytso@....edu>,
	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>, Ian Campbell <ijc@...lion.org.uk>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <wilal.deacon@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	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 V8 1/2] printk: remove tabular output for NULL pointer

Hi Joe,

thanks for your review.

On Wed, Oct 25, 2017 at 09:57:23PM -0700, Joe Perches wrote:
> On Thu, 2017-10-26 at 13:53 +1100, Tobin C. Harding wrote:
> > Currently pointer() checks for a NULL pointer argument and then if so
> > attempts to print "(null)" with _some_ standard width. This width cannot
> > correctly be ascertained here because many of the printk specifiers
> > print pointers of varying widths.
> 
> I believe this is not a good change.
> Only pointers without a <foo> extension call pointer()

Sorry, I don't understand what you mean here. All the %p<foo> specifier code is
handled by pointer()?

> > Remove the attempt to print NULL pointers with a correct width.
> 
> the correct width for a %p is the default width.

It is the default width if we are printing addresses. Once we hash 64
bit address to a 32 bit identifier then we don't have a default width.

> The correct width for %p<foo> is unknown.

I agree.

If I have misunderstood you, please forgive me. I am very appreciative
of the reviews this patch is getting and the patience the list is having
with the many iterations.

thanks,
Tobin.

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