linux-kernel - Re: [PATCH] lib/vsprintf: add %pT[C012] format specifier

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Date:	Fri, 3 Jan 2014 09:49:11 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Joe Perches <joe@...ches.com>
Cc:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Jiri Kosina <jkosina@...e.cz>,
	Al Viro <viro@...iv.linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] lib/vsprintf: add %pT[C012] format specifier

On Fri, Jan 3, 2014 at 9:39 AM, Joe Perches <joe@...ches.com> wrote:
> On Fri, 2014-01-03 at 09:08 -0800, Kees Cook wrote:
>> I'm on board with the idea of embedding comm/pid/whatever,
>
> I still think the space reduction isn't worth the
> complication.
>
>>  but I
>> either missed or do not understand why a second format-start character
>> is being added. I think this will complicate audits and maybe trigger
>> weird info leaks (imagine printing a string that was %-escaped, but
>> not 0x1A-escaped?)
>> Why not use % followed by 0x1A to be the start code, instead of just 0x1A?
>
> gcc would bleat an error for
>         "unknown conversion type character 0x1a in format".

Oh right. Bleh. Which gets me back around to the original patch which
overloaded %p.

Hrmpf. Yeah, on the fence about this.

-Kees

-- 
Kees Cook
Chrome OS Security
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