Re: [PATCH v2] integrity: nfsd imbalance bug fix

From: Andrew Morton
Date: Wed May 27 2009 - 17:09:44 EST

hugh@xxxxxxxxxxx is about to vanish - please update your address book
to hugh.dickins@xxxxxxxxxxxxxx

On Wed, 27 May 2009 09:31:52 -0400
Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx> 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?

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