linux-kernel - Re: [PATCH] kernel: escape non-ASCII and control characters in printk()

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Message-ID: <20110622190739.GB14351@albatros>
Date:	Wed, 22 Jun 2011 23:07:39 +0400
From:	Vasiliy Kulikov <segoon@...nwall.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Joe Perches <joe@...ches.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	James Morris <jmorris@...ei.org>, Ingo Molnar <mingo@...e.hu>,
	Namhyung Kim <namhyung@...il.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org,
	security@...nel.org
Subject: Re: [PATCH] kernel: escape non-ASCII and control characters in
 printk()

Hi Alan,

On Wed, Jun 22, 2011 at 19:10 +0100, Alan Cox wrote:
> If that is set you shouldn't be filtering out unicode, just control codes.

OK.

> Minor other nit is that you might want to allow BEL through and you
> certainly want to allow tab through.

In what situation do you think BEL makes sense in kernel log?  I cannot
image the situation.  Alarms should use KERN_EMERG/KERN_ALERT log level.

> The core code should not be hardcoding policy assumptions about symbol
> sets and ASCII, for an awful lot of consoles today that assumption is
> just plain wrong, for others it makes sense

No problem, I don't insist.

> So with tty maintainer hat on - NAK to the current approach but a good
> idea to do it properly.


The final check should be:

    if (iscntrl(c) && (c != '\n') && (c != '\t'))

Any comments against this variant?


Thanks,

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
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