linux-kernel - Re: [PATCH 1/3] evm: added flag IMA_NEW in the integrity_iint

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Date:	Tue, 02 Nov 2010 07:27:02 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Roberto Sassu <roberto.sassu@...ito.it>
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, James Morris <jmorris@...ei.org>,
	David Safford <safford@...son.ibm.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>
Subject: Re: [PATCH 1/3] evm: added flag IMA_NEW in the
 integrity_iint_cache structure

On Tue, 2010-11-02 at 11:05 +0100, Roberto Sassu wrote:
> The flag IMA_NEW is set in the function evm_inode_post_init_security()
> to distinguish between new and existent files and it is cleared in the
> function ima_dec_counts(). This permits to check/fix the 'security.ima'
> extended attribute properly in the function ima_appraise_measurement()
> without verifying the 'version' field of the 'integrity_iint_cache'
> structure.
> The 'i_version' field of the inode is not suitable for determining if a
> file is being created because the value '1' may be assumed by inodes
> already in the filesystem before mounting the same with the parameter
> 'iversion' as well as those newly created.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@...ito.it>

Hi Roberto.  Yes, the current patches are not differentiating an
existing file from a new one properly. I think it can be done by
replacing the 'inode->iversion == 1' test in ima_appraise_measurement()
with a test for 'inode->i_size == 0', without adding an xattr.
.
thanks,

Mimi

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