linux-kernel - Re: [PATCH v5 13/21] evm: add evm_inode_post

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Date:	Mon, 16 May 2011 11:50:51 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Steven Whitehouse <swhiteho@...hat.com>
Cc:	linux-security-module@...r.kernel.org, cluster-devel@...hat.com,
	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 13/21] evm: add evm_inode_post_init call in gfs2

On Mon, 2011-05-16 at 16:30 +0100, Steven Whitehouse wrote:
> Hi,
> 
> On Mon, 2011-05-16 at 10:45 -0400, Mimi Zohar wrote:
> > After creating the initial LSM security extended attribute, call
> > evm_inode_post_init_security() to create the 'security.evm'
> > extended attribute.
> > 
> > Signed-off-by: Mimi Zohar <zohar@...ibm.com>
> > ---
> >  fs/gfs2/inode.c |   28 +++++++++++++++++++---------
> >  1 files changed, 19 insertions(+), 9 deletions(-)
> > 
> [snip]
> > +	struct xattr lsm_xattr;
> > +	struct xattr evm_xattr;
> >  
> >  	err = security_inode_init_security(&ip->i_inode, &dip->i_inode, qstr,
> > -					   &name, &value, &len);
> > +					   &lsm_xattr.name, &lsm_xattr.value,
> > +					   &lsm_xattr.value_len);
> >  
> >  	if (err) {
> >  		if (err == -EOPNOTSUPP)
> > @@ -780,11 +781,20 @@ static int gfs2_security_init(struct gfs2_inode *dip, struct gfs2_inode *ip,
> >  		return err;
> >  	}
> >  
> > -	err = __gfs2_xattr_set(&ip->i_inode, name, value, len, 0,
> > -			       GFS2_EATYPE_SECURITY);
> > -	kfree(value);
> > -	kfree(name);
> > -
> > +	err = __gfs2_xattr_set(&ip->i_inode, lsm_xattr.name, lsm_xattr.value,
> > +			       lsm_xattr.value_len, 0, GFS2_EATYPE_SECURITY);
> > +	if (err < 0)
> > +		goto out;
> > +	err = evm_inode_post_init_security(&ip->i_inode, &lsm_xattr,
> > +					   &evm_xattr);
> > +	if (err)
> > +		goto out;
> > +	err = __gfs2_xattr_set(&ip->i_inode, evm_xattr.name, evm_xattr.value,
> > +			       evm_xattr.value_len, 0, GFS2_EATYPE_SECURITY);
> > +	kfree(evm_xattr.value);
> > +out:
> > +	kfree(lsm_xattr.name);
> > +	kfree(lsm_xattr.value);
> >  	return err;
> >  }
> >  
> 
> Just wondering whether we could have a single call to the security
> subsystem which returns a vector of xattrs rather than having to call
> two different functions?
> 
> Steve.

There are a number of places that the LSM function is called immediately
followed by either EVM/IMA.  In each of those places it is hidden from
the caller by calling the security_inode_XXX_security().  In this case
each fs has it's own method of creating an extended attribute.  If that
method could be passed to security_inode_init_security, then
security_inode_init_security() could call both the LSM and EVM functions
directly.

Mimi

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