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

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Date:	Tue, 6 Nov 2007 11:00:35 +0100
From:	Adrian Bunk <bunk@...nel.org>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	pavel@....cz, torvalds@...ux-foundation.org, darwish.07@...il.com,
	casey@...aufler-ca.com, akpm@...ux-foundation.org,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, viro@....linux.org.uk
Subject: Re: [PATCH] Smackv10: Smack rules grammar + their stateful parser

On Tue, Nov 06, 2007 at 06:56:43AM +0900, Tetsuo Handa wrote:
> 
> Linus Torvalds wrote:
> > I personally think string parsers are *much* better than the alternatives 
> > (which basically boil down to nasty binary interfaces)
> Me too.
> 
> > Binary structures and ioctl's are *much* worse. They are totally 
> > undebuggable with generic tools (think "echo" or "strace"), and they are a 
> > total nightmare to parse across architectures and pointer sizes.
> Not only pointer sizes bugs, but also checking pointer address costs.
> For binary policy, we have to examine ->next pointer is valid or not.
> We can't blindly use address supplied from userland.
> 
> I have encountered mismatch of kernel version and AppArmor's policy parser version
> when I just updated only kernel. As a result, the segmentation faults rushed toward me.
>  From this experience, TOMOYO still uses string parser in the kernel.
> If a parser doesn't consume much stack (i.e. call functions recursively), I think it is no problem.

You have a "\?" pattern which is defined as "1 byte character other
than '/'".

The user usually doesn't know how many bytes a character in a path or 
file name on his system has.

IMHO not ideal for name-based MAC...

> Thanks.


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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