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

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Date:	Tue, 6 Nov 2007 14:34:46 +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 07:49:26AM -0500, Kyle Moffett wrote:
> On Nov 06, 2007, at 07:23:36, Ahmed S. Darwish wrote:
>> On 11/6/07, Adrian Bunk <bunk@...nel.org> wrote:
>>> On Tue, Nov 06, 2007 at 01:34:05PM +0200, Ahmed S. Darwish wrote:
>>>> As far as I understand the problem now, isspace() accepts the 0xa0 
>>>> character which might collide with some of UTF-8 encoded characters 
>>>> cause the high bit is set.
>>
>> I admit I'm not experienced in such encoding stuff, but shouldn't the 
>> ASCII and the ASCII-compatible UTF-8 encodings be enough for the labels?
>>
>>> It would not work if someone would e.g. give you UTF-16 encoded strings, 
>>> but I don't see this happening in practice.
>>
>> Won't this complicate the code too much ?
>
> Well the VFS (for example) certainly doesn't support any encodings other 
> than various extended-ASCII forms (which includes UTF-8).  Something like 
> UTF-16 has extra null characters in-between every normal character, and as 
> such would fail completely if passed to the VFS.

Good point.

> Personally I think that isspace() accepting character 0xA0 is a bug, as 
> there are several variants of extended ASCII only one of which has that 
> character as a space.  Others have it as á (accented A), etc.

But even then Smack would still have a similar problem with isgraph().

> In addition 
> the "canonical" internal text format of the kernel is UTF-8 as that 
> encoding can represent any character in any other encoding and it is 
> backwards-compatible with traditional ASCII.
> 
> 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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