linux-kernel - Re: Credentials test patch

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Message-ID: <336243.38765.qm@web36610.mail.mud.yahoo.com>
Date:	Tue, 18 Sep 2007 10:58:43 -0700 (PDT)
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	Trond Myklebust <trond.myklebust@....uio.no>,
	David Howells <dhowells@...hat.com>
Cc:	viro@....linux.org.uk, hch@...radead.org,
	linux-kernel@...r.kernel.org
Subject: Re: Credentials test patch


--- Trond Myklebust <trond.myklebust@....uio.no> wrote:

> On Tue, 2007-09-18 at 17:33 +0100, David Howells wrote:
> > Hi Al, Christoph,
> > 
> > Here's a new version of my credentials patch.  It's still very basic, with
> > only Ext3, (V)FAT, NFS, AFS, SELinux and keyrings compiled in on an x86_64
> > arch kernel.  The patched kernel compiles, links and runs.
> > 
> > I've made the following major changes to the patch:
> > 
> >  (1) System calls that might want to use the credentials call
> >      update_current_cred() before calling into the VFS or whatever.  This
> >      allows the keyring pointers in the cred struct to be updated.
> > 
> >  (2) I've got rid of current_cred(), __current_cred() and the accessors for
> >      current's fsuid, fsgid and group list.  Instead you just use
> >      current->cred->whatever.  You don't need RCU to read the current
> threads
> >      credentials as only you are permitted to change them.
> > 
> > David
> > ---
> 
> What about the process' capabilities? Shouldn't they also be part of a
> credential?

As should the LSM security blob, if appropriate.

What I don't really understand is what value is gained by this exercise.
Are the savings sufficiently significant to justify the effort?


Casey Schaufler
casey@...aufler-ca.com
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