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Message-ID: <20071003205703.GM8181@ftp.linux.org.uk>
Date: Wed, 3 Oct 2007 21:57:03 +0100
From: Al Viro <viro@....linux.org.uk>
To: Casey Schaufler <casey@...aufler-ca.com>
Cc: torvalds@...l.org, linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org, akpm@...l.org, paul.moore@...com
Subject: Re: [PATCH] Version 4 (2.6.23-rc8-mm2) Smack: Simplified Mandatory Access Control Kernel
On Wed, Oct 03, 2007 at 12:51:08PM -0700, Casey Schaufler wrote:
> > > Because you throw "simple" out the window when you require userland
> > > assistance to perform this function.
> >
> > Any more than having /tmp replaced with a symlink?
>
> Yes. By the way, there's nothing that really requires that you
> use a /smack symlink if you don't want to. /tmp can still be a
> real directory, a mount point, a symlink to /var/tmp, or whatever
> else you want it to be if that suits your needs better. For the
> simplest scenarios /tmp -> /smack/tmp -> /moldy/<label> has every
> other scheme I've seen throughly beaten.
And your point is? If you don't use it, you get exact same complexity
in both setups.
> > _What_ userland intervention? Mounting stuff under /smack/tmp and not under
> > your /moldy?
>
> Who said anything about mounting under /moldy? I never did.
Sigh... So put the binding into fstab and be done with that.
> > Having /tmp replaced with symlink to /smack/tmp.link instead
> > of replacing it with a symlink to /smack/tmp?
> >
> > Absolute paths in that kind of thing are _wrong_. You know where the things
> > are on your fs. You don't know if anything else will be visible, let alone
> > whether it will be at the same place in all chroots or namespaces. And no,
> > you _can't_ make sure that fs is visible only in one place. No fs can or
> > has any business even trying.
>
> Is the objection that there is a default value coded in?
Right now the main objection is about your lack of ability to read. Which
part of "it can be mounted in different chroots/namespaces, therefore
having absolute paths doesn't work" is too hard to understand?
No, it's not about having a default. It's about keeping an absolute pathname
in virtual fs, having all instances autosoddingmatically sharing it _and_
having change attempt in any instance automatically affect all of them.
If you have that kind of sharing, don't pretend that your mechanism really
allows absolute pathnames.
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