linux-kernel - Re: ima: use of radix tree cache indexing == massive waste of memory?

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Date:	Sun, 17 Oct 2010 01:57:57 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Dave Chinner <david@...morbit.com>, linux-kernel@...r.kernel.org,
	Mimi Zohar <zohar@...ibm.com>, warthog9@...nel.org,
	hpa@...or.com, devel@...ts.fedoraprojet.org
Subject: Re: ima: use of radix tree cache indexing == massive waste of
 memory?

On Sat, 2010-10-16 at 15:20 -0400, Christoph Hellwig wrote:
> Besides the algorithmic problems with ima, why is kernel.org using
> IMA to start with?  Except for IBM looking for a reason to jusity why
> TPM isn't a completely waster of ressources it's pointless.  And it was
> only merged under the premise that it would not affect innocent normal
> users.
> 

Can we keep this at the design level please? When IMA is enabled, it
needs to store information on a per inode basis, yet has to wait to
late_initcall() for the TPM, at which point some inodes would have
already been created.  For this reason, there is a two step
initialization process, one which allocates the iints at
security_initcall() and the other which enables IMA at late_initcall().
Instead of actually allocating the iints, between security_initcall()
and late_initcall(), the original design maintained a list of inodes and
only allocated the iints if/when IMA was enabled. This design was
rejected way back when.

As for using a radix tree, that was what you recommended.

Mimi

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