[RFC 11/12] keys/mktme: Add a new key service type for memory encryption keys

On Tue, Sep 11, 2018 at 11:03:15PM +0100, David Howells wrote:

Alison Schofield [off-list ref] wrote:

quoted

+/* 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

quoted

+
+	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