SYSCALL_DEFINE5(add_key, const char __user *, _type,
		const char __user *, _description,
		const void __user *, _payload,
		size_t, plen,
		key_serial_t, ringid)
{
	key_ref_t keyring_ref, key_ref;
	char type[32], *description;
	void *payload;
	long ret;
	bool vm;

	ret = -EINVAL;
	if (plen > 1024 * 1024 - 1)
		goto error;

	/* draw all the data into kernel space */
	ret = key_get_type_from_user(type, _type, sizeof(type));
	if (ret < 0)
		goto error;

	description = strndup_user(_description, PAGE_SIZE);
	if (IS_ERR(description)) {
		ret = PTR_ERR(description);
		goto error;
	}

	/* pull the payload in if one was supplied */
	payload = NULL;

	vm = false;
	if (_payload) {
		ret = -ENOMEM;
		payload = kmalloc(plen, GFP_KERNEL);
		if (!payload) {
			if (plen <= PAGE_SIZE)
				goto error2;
			vm = true;
			payload = vmalloc(plen);
			if (!payload)
				goto error2;
		}

		ret = -EFAULT;
		if (copy_from_user(payload, _payload, plen) != 0)
			goto error3;
	}

	/* find the target keyring (which must be writable) */
	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
	if (IS_ERR(keyring_ref)) {
		ret = PTR_ERR(keyring_ref);
		goto error3;
	}

	/* create or update the requested key and add it to the target
	 * keyring */
	key_ref = key_create_or_update(keyring_ref, type, description,
				       payload, plen, KEY_PERM_UNDEF,
				       KEY_ALLOC_IN_QUOTA);
	if (!IS_ERR(key_ref)) {
		ret = key_ref_to_ptr(key_ref)->serial;
		key_ref_put(key_ref);
	}
	else {
		ret = PTR_ERR(key_ref);
	}

	key_ref_put(keyring_ref);
 error3:
	if (!vm)
		kfree(payload);
	else
		vfree(payload);
 error2:
	kfree(description);
 error:
	return ret;

} /* end sys_add_key() */