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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6E2CBC433EF for ; Tue, 15 Feb 2022 08:00:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235048AbiBOIAw convert rfc822-to-8bit (ORCPT ); Tue, 15 Feb 2022 03:00:52 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:50032 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235011AbiBOIAs (ORCPT ); Tue, 15 Feb 2022 03:00:48 -0500 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1DBF313E1B; Tue, 15 Feb 2022 00:00:38 -0800 (PST) Received: from fraeml707-chm.china.huawei.com (unknown [172.18.147.207]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4JyYLg2SbYz67ts3; Tue, 15 Feb 2022 15:56:11 +0800 (CST) Received: from fraeml714-chm.china.huawei.com (10.206.15.33) by fraeml707-chm.china.huawei.com (10.206.15.35) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Tue, 15 Feb 2022 09:00:35 +0100 Received: from fraeml714-chm.china.huawei.com ([10.206.15.33]) by fraeml714-chm.china.huawei.com ([10.206.15.33]) with mapi id 15.01.2308.021; Tue, 15 Feb 2022 09:00:35 +0100 From: Roberto Sassu To: Mimi Zohar , "shuah@kernel.org" , "ast@kernel.org" , "daniel@iogearbox.net" , "andrii@kernel.org" , "kpsingh@kernel.org" , Florent Revest CC: "linux-integrity@vger.kernel.org" , "linux-security-module@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "netdev@vger.kernel.org" , "bpf@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH] ima: Calculate digest in ima_inode_hash() if not available Thread-Topic: [PATCH] ima: Calculate digest in ima_inode_hash() if not available Thread-Index: AQHYHzTu9kKzqhEAHUiW0cSG9MzvPayRZbiAgAHZaqCAAFdHgIAArm+A Date: Tue, 15 Feb 2022 08:00:34 +0000 Message-ID: <311b5d0b3b824c548a4032a76a408944@huawei.com> References: <20220211104828.4061334-1-roberto.sassu@huawei.com> <537635732d9cbcc42bcf7be5ed932d284b03d39f.camel@linux.ibm.com> <36f85113f181f78eda3576823bd92be3f9cd1802.camel@linux.ibm.com> In-Reply-To: <36f85113f181f78eda3576823bd92be3f9cd1802.camel@linux.ibm.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.204.63.33] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected Precedence: bulk List-ID: > From: Mimi Zohar [mailto:zohar@linux.ibm.com] > Sent: Monday, February 14, 2022 11:33 PM > On Mon, 2022-02-14 at 17:05 +0000, Roberto Sassu wrote: > > > From: Mimi Zohar [mailto:zohar@linux.ibm.com] > > > Sent: Sunday, February 13, 2022 2:06 PM > > > Hi Roberto, > > > > > > On Fri, 2022-02-11 at 11:48 +0100, Roberto Sassu wrote: > > > > __ima_inode_hash() checks if a digest has been already calculated by > > > > looking for the integrity_iint_cache structure associated to the passed > > > > inode. > > > > > > > > Users of ima_file_hash() and ima_inode_hash() (e.g. eBPF) might be > > > > interested in obtaining the information without having to setup an IMA > > > > policy so that the digest is always available at the time they call one of > > > > those functions. > > > > > > > > Open a new file descriptor in __ima_inode_hash(), so that this function > > > > could invoke ima_collect_measurement() to calculate the digest if it is not > > > > available. Still return -EOPNOTSUPP if the calculation failed. > > > > > > > > Instead of opening a new file descriptor, the one from ima_file_hash() > > > > could have been used. However, since ima_inode_hash() was created to > > > obtain > > > > the digest when the file descriptor is not available, it could benefit from > > > > this change too. Also, the opened file descriptor might be not suitable for > > > > use (file descriptor opened not for reading). > > > > > > > > This change does not cause memory usage increase, due to using a > temporary > > > > integrity_iint_cache structure for the digest calculation, and due to > > > > freeing the ima_digest_data structure inside integrity_iint_cache before > > > > exiting from __ima_inode_hash(). > > > > > > > > Finally, update the test by removing ima_setup.sh (it is not necessary > > > > anymore to set an IMA policy) and by directly executing /bin/true. > > > > > > > > Signed-off-by: Roberto Sassu > > > > > > Although this patch doesn't directly modify either ima_file_hash() or > > > ima_inode_hash(), this change affects both functions. ima_file_hash() > > > was introduced to be used with eBPF. Based on Florent's post, changing > > > the ima_file_hash() behavor seems fine. Since I have no idea whether > > > anyone is still using ima_inode_hash(), perhaps it would be safer to > > > limit this behavior change to just ima_file_hash(). > > > > Hi Mimi > > > > ok. > > > > I found that just checking that iint->ima_hash is not NULL is not enough > > (ima_inode_hash() might still return the old digest after a file write). > > Should I replace that check with !(iint->flags & IMA_COLLECTED)? > > Or should I do only for ima_file_hash() and recalculate the digest > > if necessary? > > Updating the file hash after each write would really impact IMA > performance. If you really want to detect any file change, no matter > how frequently it occurs, your best bet would be to track i_generation > and i_version. Stefan is already adding "i_generation" for IMA > namespacing. I just wanted the ability to get a fresh digest after a file opened for writing is closed. Since in my use case I would not use an IMA policy, that would not be a problem. Thanks Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Zhong Ronghua > > > Please update the ima_file_hash() doc. While touching this area, I'd > > > appreciate your fixing the first doc line in both ima_file_hash() and > > > ima_inode_hash() cases, which wraps spanning two lines. > > > > Did you mean to make the description shorter or to have everything > > in one line? According to the kernel documentation (kernel-doc.rst), > > having the brief description in multiple lines should be fine. > > Thanks for checking kernel-doc. The "brief description" not wrapping > across multiple lines did in fact change. > > > > Please split the IMA from the eBPF changes. > > > > Ok. > > -- > thanks, > > Mimi