Date: Tue, 28 Mar 2006 07:53:39 -0600
From: "Serge E. Hallyn" <serue@us.ibm.com>
To: Stephen Smalley <sds@tycho.nsa.gov>
Cc: James Morris <jmorris@namei.org>, lkml <linux-kernel@vger.kernel.org>,
       linux-security-module@vger.kernel.org,
       David Howells <dhowells@redhat.com>
Subject: Re: [PATCH] split security_key_alloc into two functions
Message-ID: <20060328135339.GE19243@sergelap.austin.ibm.com>
References: <20060328130533.GB19243@sergelap.austin.ibm.com> <1143553407.3037.8.camel@moss-spartans.epoch.ncsc.mil>
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Quoting Stephen Smalley (sds@tycho.nsa.gov):
> On Tue, 2006-03-28 at 07:05 -0600, Serge E. Hallyn wrote:
> > The security_key_alloc() function acted as both an authorizer and
> > security structure allocation function.  These roles should be
> > separated.  There are two reasons for this.
> > 
> > First, if two modules are stacked, the first module might grant
> > permission and allocate security data, after which the second
> > module refuses permission.
> > 
> > Second, by adding a security_post_alloc() function after the
> > serial number has been assigned, security modules can append
> > useful info.
> 
> Are you sure that the key cannot be accessed (looked up) by another
> process as soon as it is assigned a serial number?  If it can be, then
> you risk having it accessed before its security structure is set up.

Ah, that makes sense, and even rings a bell.

So if we were to add a post_alloc() hook, it should likely go into
key_alloc_serial() under the key_serial_lock?

Still assuming that storing the serial number is desirable...

thanks,
-serge
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