netdev - Re: [Bug #11500] /proc/net bug related to selinux

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Message-ID: <m18wtpuy04.fsf@frodo.ebiederm.org>
Date:	Thu, 18 Sep 2008 11:09:31 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Stephen Smalley <sds@...ho.nsa.gov>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Moore <paul.moore@...com>, jmorris@...ei.org, rjw@...k.pl,
	linux-kernel@...r.kernel.org, kernel-testers@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [Bug #11500] /proc/net bug related to selinux

Stephen Smalley <sds@...ho.nsa.gov> writes:

> On Thu, 2008-09-18 at 08:38 -0400, Stephen Smalley wrote:
>> I do however think that the mantra that we can't require users to update
>> policy for kernel changes is unsupportable in general.  The precise set
>> of permission checks on a given operation is not set in stone and it is
>> not part of the kernel/userland interface/contract.  Policy isn't
>> "userspace"; it governs what userspace can do, and it has to adapt to
>> kernel changes.
>
> I should note here that for changes to SELinux, we have gone out of our
> way to avoid such breakage to date through the introduction of
> compatibility switches, policy flags to enable any new checks, etc
> (albeit at a cost in complexity and ever creeping compatibility code).
> But changes to the rest of the kernel can just as easily alter the set
> of permission checks that get applied on a given operation, and I don't
> think we are always going to be able to guarantee that new kernel + old
> policy will Just Work. 

I know of at least 2 more directories that I intend to turn into
symlinks into somewhere under /proc/self.  How do we keep from
breaking selinux policies when I do that?

For comparison how do we handle sysfs? 
How do we handle device nodes in tmpfs?
Ultimately do we want to implement xattrs and inotify on /proc?  
Or is there another way that would simplify maintenance?

Eric
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