linux-kernel - Re: [PATCH 2/3] integrity: Linux Integrity Module(LIM)

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Date:	Fri, 24 Oct 2008 10:47:49 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	linux-kernel@...r.kernel.org, James Morris <jmorris@...ei.org>,
	David Safford <safford@...son.ibm.com>,
	Serge Hallyn <serue@...ux.vnet.ibm.com>,
	Mimi Zohar <zohar@...ibm.com>
Subject: Re: [PATCH 2/3] integrity: Linux Integrity Module(LIM)

On Tue, 2008-10-14 at 09:28 -0400, Christoph Hellwig wrote: 
> >  int vfs_permission(struct nameidata *nd, int mask)
> >  {
> > -	return inode_permission(nd->path.dentry->d_inode, mask);
> > +	int retval;
> > +
> > +	retval = inode_permission(nd->path.dentry->d_inode, mask);
> > +	if (retval)
> > +		return retval;
> > +	return integrity_inode_permission(NULL, &nd->path,
> > +					  mask & (MAY_READ | MAY_WRITE |
> > +						  MAY_EXEC));
> >  }
> >  
> >  /**
> > @@ -306,7 +314,14 @@ int vfs_permission(struct nameidata *nd, int mask)
> >   */
> >  int file_permission(struct file *file, int mask)
> >  {
> > -	return inode_permission(file->f_path.dentry->d_inode, mask);
> > +	int retval;
> > +
> > +	retval = inode_permission(file->f_path.dentry->d_inode, mask);
> > +	if (retval)
> > +		return retval;
> > +	return integrity_inode_permission(file, NULL,
> > +					  mask & (MAY_READ | MAY_WRITE |
> > +						  MAY_EXEC));
> 
> Please don't add anything here as these two wrappers will go away.

Ok.

> Please only make decisions based on what you get in inode_permission().

Is there any way to read a file, in order to calculate a hash, based
just on an inode and a mask?  As far as I'm aware, either a file, or a
dentry and vfsmount structures, are needed.  Previously, only the
dentry, not the vfsmount, was required, which is accessible from the
inode. 

Without access to the vfsmount in inode_permission(), as
vfs_permission() is going away, the only option I see is to move the
integrity_inode_permission() call up a level to may_open(), after the
call to vfs_permission().  Would this be acceptable?  (And change the
hook name to integrity_may_open.)

Mimi

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