From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3B18EC2D0BF for ; Tue, 17 Dec 2019 22:21:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0D1CE2082E for ; Tue, 17 Dec 2019 22:21:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="WEe+w1Te" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726947AbfLQWVn (ORCPT ); Tue, 17 Dec 2019 17:21:43 -0500 Received: from linux.microsoft.com ([13.77.154.182]:40970 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726569AbfLQWVm (ORCPT ); Tue, 17 Dec 2019 17:21:42 -0500 Received: from [10.137.112.111] (unknown [131.107.147.111]) by linux.microsoft.com (Postfix) with ESMTPSA id 6E22C20B4798; Tue, 17 Dec 2019 14:21:41 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 6E22C20B4798 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1576621301; bh=9l7xQkDf03ilEjwohU/zhtjkixpnGAYFMtbXbBZSvxM=; h=From:Subject:To:Cc:References:Date:In-Reply-To:From; b=WEe+w1TeuZmWnymGKdDsY3f9DP8G7qfHy8EGMv1hOtCvhRlGy6Gmf3v9sMofUcNKK 3cyDtINBX0PEKcsTsyuAqU9gIugGq2FvqD7tHfgrT/UsGSX6w9i6b9oWjDj/AAep++ eisdpbZataBVn34Y29qsL5HzdXxLAPfRtxMb36nU= From: Lakshmi Ramasubramanian Subject: Re: [PATCH v4 2/2] IMA: Call workqueue functions to measure queued keys To: James Bottomley , zohar@linux.ibm.com, linux-integrity@vger.kernel.org Cc: eric.snowberg@oracle.com, dhowells@redhat.com, mathew.j.martineau@linux.intel.com, matthewgarrett@google.com, sashal@kernel.org, jamorris@linux.microsoft.com, linux-kernel@vger.kernel.org, keyrings@vger.kernel.org References: <20191213171827.28657-1-nramas@linux.microsoft.com> <20191213171827.28657-3-nramas@linux.microsoft.com> <1576257955.8504.20.camel@HansenPartnership.com> <39624b97-245c-ed05-27c5-588787aacc00@linux.microsoft.com> <1576423353.3343.3.camel@HansenPartnership.com> <1568ff14-316f-f2c4-84d4-7ca4c0a1936a@linux.microsoft.com> <1576479187.3784.1.camel@HansenPartnership.com> <8844a360-6d1e-1435-db7c-fd7739487168@linux.microsoft.com> <1576531022.3365.6.camel@HansenPartnership.com> <35a6c241-9a46-2657-51d1-0c04d32a9fae@linux.microsoft.com> Message-ID: <152580f3-2a1f-fa33-cc25-f25747a470a5@linux.microsoft.com> Date: Tue, 17 Dec 2019 14:22:07 -0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi James, >>> >>> This is the problem: in the race case you may still be adding keys to >>> the queue after the other thread has processed it. Those keys won't get >>> processed because the flag is now false in the post check so the >>> current thread won't process them either. >>> >>> James >>> Please let me know if you still think there is a race condition. If yes, please explain how a key would be added to the queue after ima_process_queued_keys() has processed queued keys. ima_process_keys flag will be true when queued keys have been processed. > > Please keep in mind that ima_queue_key() returns a boolean indicating > whether or not the key was queued. This flag is set inside the lock - > please see the code snippet from ima_queue_key() below: > > +    mutex_lock(&ima_keys_mutex); > +    if (!ima_process_keys) { > +        list_add_tail(&entry->list, &ima_keys); > +        queued = true; > +    } > +    mutex_unlock(&ima_keys_mutex); > > If ima_process_keys had changed from false to true, ima_queue_key() will > not queue the key and return false to ima_post_key_create_or_update(). > > Code snippet in ima_post_key_create_or_update(): > > +    if (!ima_process_keys) > +        queued = ima_queue_key(keyring, payload, payload_len); > + > +    if (queued) > +        return; > > If the "queued" is false, ima_post_key_create_or_update() will process > the key immediately. > >  -lakshmi thanks, -lakshmi