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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 2B57DC433F4 for ; Mon, 24 Sep 2018 17:53:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E85C72098A for ; Mon, 24 Sep 2018 17:53:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E85C72098A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731724AbeIXX45 (ORCPT ); Mon, 24 Sep 2018 19:56:57 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:42373 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728999AbeIXX44 (ORCPT ); Mon, 24 Sep 2018 19:56:56 -0400 Received: from fsav109.sakura.ne.jp (fsav109.sakura.ne.jp [27.133.134.236]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id w8OHrCSC021129; Tue, 25 Sep 2018 02:53:12 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav109.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav109.sakura.ne.jp); Tue, 25 Sep 2018 02:53:12 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav109.sakura.ne.jp) Received: from [192.168.1.8] (softbank060157066051.bbtec.net [60.157.66.51]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id w8OHrC8t021126 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Tue, 25 Sep 2018 02:53:12 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH v4 00/19] LSM: Module stacking for SARA and Landlock To: Casey Schaufler , Kees Cook Cc: LSM , James Morris , SE Linux , LKLM , John Johansen , Paul Moore , Stephen Smalley , "linux-fsdevel@vger.kernel.org" , Alexey Dobriyan , =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= , Salvatore Mesoraca References: <680e6e16-0890-8304-0e8e-6c58966813b5@schaufler-ca.com> <39457e79-3816-824b-6b4d-89d21b03f9ce@i-love.sakura.ne.jp> <3350edec-c233-9428-73b0-58d582d1e3b9@schaufler-ca.com> From: Tetsuo Handa Message-ID: Date: Tue, 25 Sep 2018 02:53:12 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <3350edec-c233-9428-73b0-58d582d1e3b9@schaufler-ca.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/09/25 2:16, Casey Schaufler wrote: >> Not all of LKM-based LSMs use security blobs. And some of LKM-based LSMs >> might use security blobs for only a few objects. For example, AKARI uses >> inode security blob for remembering whether source address/port of an >> accept()ed socket was already checked, only during accept() operation and >> first socket operation on the accept()ed socket. Thus, there is no need >> to waste memory by assigning blobs for all inode objects. > > The first question is why use an inode blob? Shouldn't you > be using a socket blob for this socket based information? Indeed. AKARI can as well use security_sk_free() using address of "struct sock" as a key. > > If you only want information part of the time you can declare > a pointer sized blob and manage what hangs off that as you will. > I personally think that the added complexity of conditional > blob management is more pain than it's worth, but if you want > a really big blob, but only on occasion, I could see doing it. LKM based LSMs are too late for updating blob_sizes.* fields. Even if they could, they after all have to somehow check whether corresponding init hook was called. That's checking for NULL. >> >>>> @@ -1202,11 +1183,11 @@ void security_file_free(struct file *file) >>>> { >>>> void *blob; >>>> >>>> + call_void_hook(file_free_security, file); >>>> + >>>> if (!lsm_file_cache) >>>> return; >>>> >>>> - call_void_hook(file_free_security, file); >>>> - >>> Why does this make sense? If the lsm_file_cache isn't >>> initialized you can't have allocated any file blobs, >>> no module can have initialized a file blob, hence there >>> can be nothing for the module to do. >>> >> For modules (not limited to LKM-based LSMs) which want to use >> file blobs for only a few objects and avoid wasting memory by >> allocating file blobs to all file objects. >> >> Infrastructure based blob management fits well for LSM modules >> which want to assign blobs to all objects (like SELinux). But >> forcing infrastructure based blob management can become a huge >> waste of memory for LSM modules which want to assign blobs to >> only a few objects. Unconditionally calling file_free_security >> hook (as with other hooks) preserves a room for allowing the >> latter type of LSM modules without using infrastructure based >> blob management. > > There is a hypothetical issue here, but that would require abuse > of the infrastructure. Having a file_free_security hook that doesn't > free a security blob allocated by file_alloc_security may coincidentaly > be useful, but that's not the intent of the hook. > The free hook might be used for freeing resources which were not allocated by alloc hook. Yama is using task_free hook without task_alloc hook. Someone might want to use file_free hook without file_alloc hook.