linux-kernel - Re: [PATCH v5 05/21] ima: move ima_file

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Message-ID: <1305852901.2528.40.camel@localhost.localdomain>
Date:	Thu, 19 May 2011 20:55:01 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	James Morris <jmorris@...ei.org>,
	David Safford <safford@...son.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg KH <greg@...ah.com>,
	Dmitry Kasatkin <dmitry.kasatkin@...ia.com>,
	Mimi Zohar <zohar@...ibm.com>
Subject: Re: [PATCH v5 05/21] ima: move ima_file_free before releasing the
 file

On Thu, 2011-05-19 at 17:06 -0500, Serge E. Hallyn wrote:
> Quoting Mimi Zohar (zohar@...ux.vnet.ibm.com):
> > Integrity appraisal measures files on file_free and stores the file
> > measurement as an xattr.  Measure the file before releasing it.
> 
> Can you put a bit more in the commit msg about why?  What's magic
> about the fs-specific release function?

ima_file_free(), called on __fput(), currently flags files that have
changed, so that the file is re-measured.  However, for appraising a
files's integrity, flagging the file is not enough.  The file's
security.ima xattr must be updated to reflect any changes.  This patch
moves releasing the file to after calculating the new file hash.

> > Signed-off-by: Mimi Zohar <zohar@...ibm.com>
> > Acked-by: Serge Hallyn <serge.hallyn@...ntu.com>
> > ---
> >  fs/file_table.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/fs/file_table.c b/fs/file_table.c
> > index 01e4c1e..33f54a1 100644
> > --- a/fs/file_table.c
> > +++ b/fs/file_table.c
> > @@ -243,10 +243,10 @@ static void __fput(struct file *file)
> >  		if (file->f_op && file->f_op->fasync)
> >  			file->f_op->fasync(-1, file, 0);
> >  	}
> > +	ima_file_free(file);
> >  	if (file->f_op && file->f_op->release)
> >  		file->f_op->release(inode, file);
> >  	security_file_free(file);
> > -	ima_file_free(file);
> >  	if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
> >  		     !(file->f_mode & FMODE_PATH))) {
> >  		cdev_put(inode->i_cdev);
> > -- 

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