linux-kernel - Re: [PATCH] Smackv10: Smack rules grammar + their stateful parser

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Message-ID: <20071106085651.GC26163@stusta.de>
Date:	Tue, 6 Nov 2007 09:56:51 +0100
From:	Adrian Bunk <bunk@...nel.org>
To:	Kyle Moffett <mrmacman_g4@....com>
Cc:	"Ahmed S. Darwish" <darwish.07@...il.com>,
	Casey Schaufler <casey@...aufler-ca.com>, akpm@...l.org,
	torvalds@...l.org, linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Smackv10: Smack rules grammar + their stateful parser

On Tue, Nov 06, 2007 at 03:26:12AM -0500, Kyle Moffett wrote:
> On Nov 06, 2007, at 01:33:05, Adrian Bunk wrote:
>> Can you limit this to 7bit ASCII and use isascii() somewhere?
>>
>> Otherwise I'd expect funny things to happen when you e.g. use isspace() on 
>> the UTF-8 encoded character à.
>
> Actually, you don't need to.  You tell them it expects UTF-8 encoded 
> strings and be done with it.  All US-ASCII characters from 0 through 127 
> (IE: high bit clear) are exactly the same in UTF-8, and UTF-8 special 
> characters have the high bit set in all bytes.  Therefore you just assume 
> that anything with the high bit set is part of a word and you can handle 
> basic UTF-8.  (It doesn't work on special UTF-8 space characters like 
> nonbreaking space and similar, but handling those is significantly more 
> complicated).

The documentations says:
"Smack labels cannot contain unprintable characters or the "/" (slash) 
 character."

What you propose might contain unprintable characters, and it might even 
be invalid UTF-8.

> Cheers,
> Kyle Moffett

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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