linux-kernel - Re: [PATCH 2/2] Version 9 (2.6.24-rc1) Smack: Simplified Mandatory Access Control Kernel

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Date:	Sat, 27 Oct 2007 22:41:49 -0700 (PDT)
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	Al Viro <viro@....linux.org.uk>,
	"Ahmed S. Darwish" <darwish.07@...il.com>
Cc:	casey@...aufler-ca.com, akpm@...l.org, torvalds@...l.org,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] Version 9 (2.6.24-rc1) Smack: Simplified Mandatory Access Control Kernel


--- Al Viro <viro@....linux.org.uk> wrote:

> On Sat, Oct 27, 2007 at 11:01:12AM +0200, Ahmed S. Darwish wrote:
> > The problem here (As discussed in private mails) is that the for loop 
> > assumes that the beginning of given user-space buffer is the beginning
> > of a rule. This leads to situations where the rule becomes "ecret 20",
> > or "cret 20" instead of "Secret 20". Big input buffers/files leads 
> > smack to recieve a rule like "Secret 20" in fragmented chunks like:
> > 
> > write("<lots of rules before ours>\nSec", ..)
> > write("r", 1, ..)
> > write("et 20\n<remaing rules after ours>", ..)
> > 
> > Parsing a rule in such tough conditions in _kernel space_ is very
> > hard. I began to feel that it will be much easier if we do the parsing 
> > in a userspace utility and let smack accept only small buffers (80 char). 
> 
> For crying out louf, all it takes is a finite state machine...  BTW, folks,
> your parser *and* input language suck.  Really.  Silently allowing noise
> is Dumb(tm).

I was planning to patient Dumb, but if you've already got a copywrite
on it I'll have to go a different route. Carp.

> Please, write the grammar down and _follow_ _it_.

Good idea. I'll do it.

>  ...
> 
> Come on, people, this is ridiculous - why bother reinventing the wheels for
> the stuff that belongs to exercises halfway through any self-respecting
> introductory textbook?  Scary parser, my arse...

That code is in need of cleansing. With bleach. Yes, it's on my list.
I managed to get my virtual disk back, found how I messed up on v9,
and now have a (long) list of improvements and fixes.

No rest for the wicked.


Casey Schaufler
casey@...aufler-ca.com
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