linux-kernel - Re: [RFC][Patch 2/6] integrity: fs hook placement

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Date:	Thu, 08 Mar 2007 13:34:42 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Chris Wright <chrisw@...s-sol.org>
Cc:	"Serge E. Hallyn" <serue@...ibm.com>, linux-kernel@...r.kernel.org,
	safford@...son.ibm.com, serue@...ux.vnet.ibm.com,
	kjhall@...ux.vnet.ibm.com, zohar@...ibm.com
Subject: Re: [RFC][Patch 2/6] integrity: fs hook placement

On Thu, 2007-03-08 at 09:40 -0800, Chris Wright wrote:
> * Serge E. Hallyn (serue@...ibm.com) wrote:
> > Are you objecting only to the duplication at the callsites, so that an
> > fsnotify-type of consolidation of security and integrity hooks would be
> > ok?  Or are you complaining that the security_inode_setxattr and
> > integrity_inode_setxattr hooks are too similar anyway, and integrity
> > modules should just use some lsm hooks for anything which will be
> > authoritative?
> 
> It's duplication of callsites with many identical implementations
> that's the problem.
>
> > (I could see an argument that integirty subsystem should be purely for
> > measuring and hence its hooks should never return a value.  Only hitch
> > there is that if integrity subsystem hits ENOMEM it should be able to
> > refuse the action...)
> 
> Right, that's what I was expecting to see, just the measurement
> infrastructure.

There are a total of 10 Linux Integrity Module(LIM) hooks. Seven of
which parallel the LSM hooks, out of the ~150 LSM hooks.  3 of the LIM
hooks are for initializing, allocating, and freeing the inode-
>i_integrity, used for caching integrity information.  As the integrity
information is stored as extended attributes, 2 hooks are for catching
changes to the extended attributes, one is for updating the extended
attributes when the file closes, and d_instantiate is used for
initialization.  Is this excessive?  How else would you design
integrity, without using the LSM hooks?

Mimi Zohar


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