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Date: Tue, 11 Sep 2018 15:39:33 -0700
From: Alison Schofield <alison.schofield@intel.com>
Subject: Re: [RFC 11/12] keys/mktme: Add a new key service type for memory
 encryption keys
Message-ID: <20180911223933.GA2638@alison-desk.jf.intel.com>
References: <1a14a6feb02f968c5e6b98360f6f16106b633b58.1536356108.git.alison.schofield@intel.com>
 <cover.1536356108.git.alison.schofield@intel.com>
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To: David Howells <dhowells@redhat.com>
Cc: tglx@linutronix.de, Kai Huang <kai.huang@intel.com>, Jun Nakajima <jun.nakajima@intel.com>, Kirill Shutemov <kirill.shutemov@intel.com>, Dave Hansen <dave.hansen@intel.com>, Jarkko Sakkinen <jarkko.sakkinen@intel.com>, jmorris@namei.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, linux-mm@kvack.org

On Tue, Sep 11, 2018 at 11:03:15PM +0100, David Howells wrote:
> Alison Schofield <alison.schofield@intel.com> wrote:
> 
> > +/* Key Service Command: Creates a software key and programs hardware */
> > +int mktme_instantiate(struct key *key, struct key_preparsed_payload *prep)
> > +{
> > +	struct mktme_key_program *kprog = NULL;
> > +	size_t datalen = prep->datalen;
> > +	char *options;
> > +	int ret = 0;
> > +
> > +	if (!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
> > +		return -EACCES;
> > +
> > +	if (datalen <= 0 || datalen > 1024 || !prep->data)
> > +		return -EINVAL;
> > +
> > +	options = kmemdup(prep->data, datalen + 1, GFP_KERNEL);
> > +	if (!options)
> > +		return -ENOMEM;
> > +
> > +	options[datalen] = '\0';
> > +
> > +	kprog = kmem_cache_zalloc(mktme_prog_cache, GFP_KERNEL);
> > +	if (!kprog) {
> > +		kzfree(options);
> > +		return -ENOMEM;
> > +	}
> > +	ret = mktme_get_options(options, kprog);
> > +	if (ret < 0)
> > +		goto out;
> 
> Everything prior to here looks like it should be in the ->preparse() routine.
> I really should get round to making that mandatory.

Hi Dave,

If a preparse routine handles all the above, then if any of the
above failures occur, the key service has less backing out to do.
Is that the point?

How do I make the connection between the preparse and the instantiate? 
Do I just put what I need to remember about this key request in the
payload.data during preparse, so I can examine it again during
instantiate?

Thanks,
Alison

> 
> > +
> > +	mktme_map_lock();
> > +	ret = mktme_program_key(key->serial, kprog);
> > +	mktme_map_unlock();
> > +out:
> > +	kzfree(options);
> > +	kmem_cache_free(mktme_prog_cache, kprog);
> > +	return ret;
> > +}
> 
> David