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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 9DF7EC4727E for ; Thu, 24 Sep 2020 20:54:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5B3F722208 for ; Thu, 24 Sep 2020 20:54:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726666AbgIXUy3 (ORCPT ); Thu, 24 Sep 2020 16:54:29 -0400 Received: from mga02.intel.com ([134.134.136.20]:32990 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726242AbgIXUy2 (ORCPT ); Thu, 24 Sep 2020 16:54:28 -0400 IronPort-SDR: PUDwTVxlA6/VZz7h4A2EW44zLNbzSr9AAL1WuNSDlJspmFA6ZkIXYmeIEbXGxnWkEpAPIBUvPM RxA9AOnq5zUg== X-IronPort-AV: E=McAfee;i="6000,8403,9754"; a="149001151" X-IronPort-AV: E=Sophos;i="5.77,299,1596524400"; d="scan'208";a="149001151" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Sep 2020 13:54:13 -0700 IronPort-SDR: 3kQXzppf/+QXio/EcoVKWPNnv7ZQ8SQuqXjQA2MLcHfZi2bztFE/kxVXJ1waIp2jcaCyHrUKF0 G6LHd7OzI5Cw== X-IronPort-AV: E=Sophos;i="5.77,299,1596524400"; d="scan'208";a="487100000" Received: from ejarlos-mobl.amr.corp.intel.com (HELO [10.212.15.103]) ([10.212.15.103]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Sep 2020 13:54:10 -0700 Subject: Re: [PATCH v38 10/24] mm: Add vm_ops->mprotect() To: Sean Christopherson Cc: Haitao Huang , Jarkko Sakkinen , 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, "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 References: <20200921211849.GA25403@linux.intel.com> <20200922052957.GA97272@linux.intel.com> <20200922053515.GA97687@linux.intel.com> <20200922164301.GB30874@linux.intel.com> <20200923135056.GD5160@linux.intel.com> <20200924192853.GA18826@linux.intel.com> <20200924200156.GA19127@linux.intel.com> <20200924202549.GB19127@linux.intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200924202549.GB19127@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/24/20 1:25 PM, Sean Christopherson wrote: ... >> Why don't we just declare enclave memory as "out of scope for noexec" in >> the same way that anonymous memory is, and just discard this patch? >> That doesn't seem too much of a stretch. > > Because we lose line of sight to LSM support. Without enforcing "declare perms > at load time" in the initial series, we would create an ABI where userspace > could load an enclave page with only READ permissions and then map the enclave > with whatever permissions it wants, without any convenient way for SGX to call > into the LSM. This argument holds no water for me. LSMs are all about taking what would otherwise be perfectly acceptable behavior and breaking them in the name of security. They fundamentally break applications that used to work just fine and also did totally sane things. > Retroactively enforcing permissions at load time would break the ABI, or at > least yield different behavior based on the mere existence of LSMs, e.g. if > LSMs are supported, suddenly the ADD_PAGES w/ READ -> mmap(RWX) flow breaks, > even if there is no LSM policy denying that behavior. I'm a security dummy. All I know is that when I see something like this: if (security_vm_enough_memory_mm(mm, grow)) ... I know to ignore it because I like my systems to boot and I'm not using those hooks. :) How could the mere presence of an LSM change the behavior of one of these hooks? Don't they have to actually hook into the specific place and actively go trying to change the behavior at that site?