linux-kernel - Re: [PATCH 3/4] integrity: Linux Integrity Module(LIM)

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Message-ID: <OFAC0E3107.C68382CD-ON852574A2.0068E1AD-852574A2.00692623@us.ibm.com>
Date:	Mon, 11 Aug 2008 15:08:36 -0400
From:	Mimi Zohar <zohar@...ibm.com>
To:	serue@...ux.vnet.ibm.com
Cc:	Christoph Hellwig <hch@...radead.org>,
	James Morris <jmorris@...ei.org>, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	Randy Dunlap <randy.dunlap@...cle.com>, safford@...son.ibm.com,
	sailer@...son.ibm.com, Stephen Smalley <sds@...ho.nsa.gov>,
	serue@...ux.vnet.ibm.com, Al Viro <viro@...IV.linux.org.uk>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Subject: Re: [PATCH 3/4] integrity: Linux Integrity Module(LIM)

serue@...ux.vnet.ibm.com wrote on 08/11/2008 01:02:55 PM:

> Quoting Mimi Zohar (zohar@...ibm.com):
> > Christoph Hellwig <hch@...radead.org> wrote on 08/09/2008 02:53:40 PM:
> > > >  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 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 put your hook into inode_permission.  Note that in inode
> > > permission and lots of callers there is no path available so don't 
pass
> > > it.  Please pass the full MAY_FOO mask for new interfaces and do
> > > filtering that won't break if new ones are introduced.
> > 
> > We started out with the integrity_inode_permission() hook call in 
> > inode_permission(), but because of the removal of the nameidata 
> > parameter in the last merge, based on discussions
> > http://marc.info/?l=linux-security-module&m=121797845308246&w=2,
> > the call to integrity_inode_permission() was moved up to the caller,
> > where either a file or path are available.  Any suggestions?
> 
> Mimi, can you explain exactly (and concisely) what you are doing with
> the pathname?

IMA maintains a list of hash values of system sensitive files loaded 
into the run-time of the system and extends a PCR with the hash value. 
In order to calculate this hash value, IMA requires access to either
the file or the path, which currently is not accessible in 
inode_permission().

Mimi
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