linux-kernel - Re: [PATCH v2] integrity: nfsd imbalance bug fix

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Date:	Wed, 27 May 2009 14:09:15 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, hooanon05@...oo.co.jp,
	"J. Bruce Fields" <bfields@...ldses.org>,
	James Morris <jmorris@...ei.org>,
	David Safford <safford@...son.ibm.com>,
	linux-nfs@...r.kernel.org, Mimi Zohar <zohar@...ibm.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>
Subject: Re: [PATCH v2] integrity: nfsd imbalance bug fix


hugh@...itas.com is about to vanish - please update your address book
to hugh.dickins@...cali.co.uk.

On Wed, 27 May 2009 09:31:52 -0400
Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:

> An nfsd exported file is opened/closed by the kernel causing the
> integrity imbalance message.
> 
> Before a file is opened, there normally is permission checking, which
> is done in inode_permission().  However, as integrity checking requires
> a dentry and mount point, which is not available in inode_permission(),
> the integrity (permission) checking must be called separately.
> 
> In order to detect any missing integrity checking calls, we keep track
> of file open/closes.  ima_path_check() increments these counts and
> does the integrity (permission) checking. As a result, the number of
> calls to ima_path_check()/ima_file_free() should be balanced.  An extra
> call to fput(), indicates the file could have been accessed without first
> calling ima_path_check().
> 
> In nfsv3 permission checking is done once, followed by multiple reads,
> which do an open/close for each read.  The integrity (permission) checking
> call should be in nfsd_permission() after the inode_permission() call, but
> as there is no correlation between the number of permission checking and
> open calls, the integrity checking call should not increment the counters,
> but defer it to when the file is actually opened.
> 
> This patch adds:
> - integrity (permission) checking for nfsd exported files in nfsd_permission().
> - a call to increment counts for files opened by nfsd.
> 
> This patch has been updated to return the nfs error types.

I have a note here that Hugh had some significant issues with the
previous version of this patch.

Were these problems addressed?  If so, how?

Thanks.
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