linux-kernel - Re: [AppArmor 39/45] AppArmor: Profile loading and manipulation, pathname matching

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Date:	Thu, 14 Jun 2007 17:18:43 -0700 (PDT)
From:	david@...g.hm
To:	Jack Stone <jack@...keye.stone.uk.eu.org>
cc:	greg@...ah.com, agruen@...e.de, sds@...ho.nsa.gov,
	jjohansen@...e.de, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, pavel@....cz
Subject: Re: [AppArmor 39/45] AppArmor: Profile loading and manipulation,
 pathname matching

On Thu, 14 Jun 2007, Jack Stone wrote:

> david@...g.hm wrote:
>> On Sun, 10 Jun 2007, Pavel Machek wrote:
>>> But you have that regex in _user_ space, in a place where policy
>>> is loaded into kernel.
>>
>> then the kernel is going to have to call out to userspace every time a
>> file is created or renamed and the policy is going to be enforced
>> incorrectly until userspace finished labeling/relabeling whatever is
>> moved. building this sort of race condigion for security into the kernel
>> is highly questionable at best.
>>
>>> AA has regex parser in _kernel_ space, which is very wrong.
>>
>> see Linus' rants about why it's not automaticaly the best thing to move
>> functionality into userspace.
>>
>> remember that the files covered by an AA policy can change as files are
>> renamed. this isn't the case with SELinux so it doesn't have this sort
>> of problem.
>
> How about using the inotify interface on / to watch for file changes and
> updating the SELinux policies on the fly. This could be done from a
> userspace daemon and should require minimal SELinux changes.
>
> The only possible problems I can see are the (hopefully) small gap
> between the file change and updating the policy and the performance
> problems of watching the whole system for changes.

as was mentioned by someone else, if you rename a directory this can 
result in millions of files that need to be relabeled (or otherwise have 
the policy changed for them)

that can take a significant amount of time to do.

David Lang
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