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

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Date:	Tue, 6 Nov 2007 07:49:26 -0500
From:	Kyle Moffett <mrmacman_g4@....com>
To:	"Ahmed S. Darwish" <darwish.07@...il.com>
Cc:	Adrian Bunk <bunk@...nel.org>,
	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 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.

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.   
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-
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