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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 DB076C35257 for ; Mon, 21 Sep 2020 21:18:57 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 74D8123A5C for ; Mon, 21 Sep 2020 21:18:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 74D8123A5C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id F1CB16B00E7; Mon, 21 Sep 2020 17:18:56 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id ECBCD6B00E8; Mon, 21 Sep 2020 17:18:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D93C48E0001; Mon, 21 Sep 2020 17:18:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0179.hostedemail.com [216.40.44.179]) by kanga.kvack.org (Postfix) with ESMTP id BDC8F6B00E7 for ; Mon, 21 Sep 2020 17:18:56 -0400 (EDT) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 73C97181AC9BF for ; Mon, 21 Sep 2020 21:18:56 +0000 (UTC) X-FDA: 77288333472.20.juice65_171793227148 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin20.hostedemail.com (Postfix) with ESMTP id 5304C180C07A3 for ; Mon, 21 Sep 2020 21:18:56 +0000 (UTC) X-HE-Tag: juice65_171793227148 X-Filterd-Recvd-Size: 5938 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by imf02.hostedemail.com (Postfix) with ESMTP for ; Mon, 21 Sep 2020 21:18:54 +0000 (UTC) IronPort-SDR: BQMc6Xzt0BpR9CfLmCQqJMwYoa5VA+gUpUWAskoVUhgH3E9c+JwvEFP8aEtAQ+CAgBJm9opLDK vT/QfvXQ3arw== X-IronPort-AV: E=McAfee;i="6000,8403,9751"; a="159769553" X-IronPort-AV: E=Sophos;i="5.77,288,1596524400"; d="scan'208";a="159769553" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2020 14:18:51 -0700 IronPort-SDR: gpMzqasrgDOlunN7o47es6wodaUU1K4jOZ0/VcEWxyI9wLagCpb8B7ZqSYTDs5MMLS+wr/u2HK f9Tpb58uu1Nw== X-IronPort-AV: E=Sophos;i="5.77,288,1596524400"; d="scan'208";a="485669996" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.160]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Sep 2020 14:18:50 -0700 Date: Mon, 21 Sep 2020 14:18:49 -0700 From: Sean Christopherson To: Jarkko Sakkinen Cc: Andy Lutomirski , X86 ML , linux-sgx@vger.kernel.org, LKML , Linux-MM , Andrew Morton , Matthew Wilcox , Jethro Beekman , Darren Kenny , Andy Shevchenko , asapek@google.com, Borislav Petkov , "Xing, Cedric" , chenalexchen@google.com, Conrad Parker , cyhanish@google.com, Dave Hansen , "Huang, Haitao" , Josh Triplett , "Huang, Kai" , "Svahn, Kai" , Keith Moyer , Christian Ludloff , Neil Horman , Nathaniel McCallum , Patrick Uiterwijk , David Rientjes , Thomas Gleixner , yaozhangx@google.com Subject: Re: [PATCH v38 10/24] mm: Add vm_ops->mprotect() Message-ID: <20200921211849.GA25403@linux.intel.com> References: <20200915112842.897265-1-jarkko.sakkinen@linux.intel.com> <20200915112842.897265-11-jarkko.sakkinen@linux.intel.com> <20200918235337.GA21189@sjchrist-ice> <20200921124946.GF6038@linux.intel.com> <20200921165758.GA24156@linux.intel.com> <20200921210736.GB58176@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200921210736.GB58176@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Sep 22, 2020 at 12:07:36AM +0300, Jarkko Sakkinen wrote: > On Mon, Sep 21, 2020 at 09:57:58AM -0700, Sean Christopherson wrote: > > On Mon, Sep 21, 2020 at 03:49:46PM +0300, Jarkko Sakkinen wrote: > > > On Fri, Sep 18, 2020 at 04:53:37PM -0700, Sean Christopherson wrote: > > > > a noexec filesystem by loading code into an enclave, and to give the kernel the > > > > option of adding enclave specific LSM policies in the future. > > > > > > > > The source file (if one exists) for the enclave is long gone when the enclave > > > > is actually mmap()'d and mprotect()'d. To enforce noexec, the requested > > > > permissions for a given page are snapshotted when the page is added to the > > > > enclave, i.e. when the enclave is built. Enclave pages that will be executable > > > > must originate from an a MAYEXEC VMA, e.g. the source page can't come from a > > > > noexec file system. > > > > > > noexec check is done in __sgx_encl_add_page(), not in this callback. > > > sgx_vma_mprotect() calls sgx_encl_may_map(), which iterates the > > > addresses, checks that permissions are not surpassed and there are > > > no holes. > > > > Yes, that's what I said. > > sgx_encl_add_page() will remove such page. The callback does not > interact with this process as such pages never get to the enclave. I think we're in violent agreement, mostly. Userspace can add the page without EXEC permissions in the EPCM, and thus avoid the noexec/VM_MAYEXEC check. The enclave can then do EMODPE to gain EXEC permissions in the EPMC. Without the ->mprotect() hook, we wouldn't be able to detect/prevent such shenanigans. > > I would copy-paste the part of the response that was snipped... > > I do agree with the main conclusions but it contains also things that I > do not see relating that much, like noexec partitions. As above, this does directly related to noexec/VM_MAYEXEC. > It goes too far in detail what will LSM's end up doing. I absolutely do not > want to forecast too far how LSM hooks would work. That's fine, I was responding to Andy's question, not intending to write a changelog. > Since we do not have ioctl's for EMODPE and such, I see EMODPE as the > only reason for doing this right now. Otherwise, we are in trouble with > any possible LSM callbacks. For any sort of access control decision, > things decided must stick. Yes, again, violent agreement :-). > I would add something like this to the commit message largely based on > your text: > > "SGX stores the permissions for each page when they are first added, and > will implement this callback to check that mmap() or mprotect() does not > surpass these permissions in the requested address range. > > This is done to prevent using EMODPE upgrading permissions of a page > after mmap() or mprotect() has been done, which would prevent any sort > of LSM callbacks to be implemented later on because the access control > decision could deprecate."