linux-kernel - Re: [RFC][PATCH 3/7] smack: assign the label set in file->f

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Message-Id: <201104281006.05629.roberto.sassu@polito.it>
Date:	Thu, 28 Apr 2011 10:06:05 +0200
From:	Roberto Sassu <roberto.sassu@...ito.it>
To:	Casey Schaufler <casey@...aufler-ca.com>
Cc:	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	dhowells@...hat.com, jmorris@...ei.org, zohar@...ux.vnet.ibm.com,
	safford@...son.ibm.com, tyhicks@...ux.vnet.ibm.com,
	kirkland@...onical.com, ecryptfs-devel@...ts.launchpad.net,
	eparis@...hat.com, sds@...ho.nsa.gov, selinux@...ho.nsa.gov,
	viro@...iv.linux.org.uk
Subject: Re: [RFC][PATCH 3/7] smack: assign the label set in file->f_cred to new file descriptors

On Thursday, April 28, 2011 01:26:43 AM Casey Schaufler wrote:
> On 4/27/2011 5:34 AM, Roberto Sassu wrote:
> > The SMACK label of new file descriptors is obtained from the credentials
> > set in the 'f_cred' field of the same structure.
> >
> > Signed-off-by: Roberto Sassu <roberto.sassu@...ito.it>
> > ---
> >  security/smack/smack_lsm.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> > index c6f8fca..e3c9e54 100644
> > --- a/security/smack/smack_lsm.c
> > +++ b/security/smack/smack_lsm.c
> > @@ -1011,7 +1011,7 @@ static int smack_file_permission(struct file *file, int mask)
> >   */
> >  static int smack_file_alloc_security(struct file *file)
> >  {
> > -	file->f_security = smk_of_current();
> > +	file->f_security = smk_of_task(file->f_cred->security);
> 
> Now hang on. This just looks wrong. You're setting the value of one
> field of the file structure to another value in the same file structure.
> I don't see that this is what I want.
> 

Hi Casey

thanks for the review.
The field 'f_cred' stores the credentials of the subject that issued the open.
The first patch allows to set this field with the credentials provided to
the function get_empty_filp() which may be those of the 'current'
process as in the original case, or those provided by a kernel service that
called the function dentry_open() directly.

Roberto Sassu


> >  	return 0;
> >  }
> >  
> 
> 
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