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 173AEC4727D for ; Tue, 22 Sep 2020 16:43:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B2D7220738 for ; Tue, 22 Sep 2020 16:43:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B2D7220738 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 20C4F900025; Tue, 22 Sep 2020 12:43:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1BBEB900003; Tue, 22 Sep 2020 12:43:08 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 08487900025; Tue, 22 Sep 2020 12:43:08 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0051.hostedemail.com [216.40.44.51]) by kanga.kvack.org (Postfix) with ESMTP id E15CC900003 for ; Tue, 22 Sep 2020 12:43:07 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id A52921EE6 for ; Tue, 22 Sep 2020 16:43:07 +0000 (UTC) X-FDA: 77291267214.03.baby38_000156d2714f Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin03.hostedemail.com (Postfix) with ESMTP id 7878928A4EA for ; Tue, 22 Sep 2020 16:43:07 +0000 (UTC) X-HE-Tag: baby38_000156d2714f X-Filterd-Recvd-Size: 4804 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by imf16.hostedemail.com (Postfix) with ESMTP for ; Tue, 22 Sep 2020 16:43:06 +0000 (UTC) IronPort-SDR: y1G0xIy3BCED4JrzkWmJjG5KeMEiUkMXXYbiGcSREqUmdrQUqYjsqRDjtRWwzPZ6cSLLIptz6b q3kwW4mpaUnQ== X-IronPort-AV: E=McAfee;i="6000,8403,9752"; a="140662934" X-IronPort-AV: E=Sophos;i="5.77,291,1596524400"; d="scan'208";a="140662934" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2020 09:43:04 -0700 IronPort-SDR: 4oSWxbAXMAdIjFSfeAITRunkFUGcGO10gjSXJM/fC/GptPlBIhLFx0AbArKAFk2jKBb8H5RNPl +Q7JSufRXtkw== X-IronPort-AV: E=Sophos;i="5.77,291,1596524400"; d="scan'208";a="342086235" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.160]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2020 09:43:04 -0700 Date: Tue, 22 Sep 2020 09:43:02 -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: <20200922164301.GB30874@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> <20200921211849.GA25403@linux.intel.com> <20200922052957.GA97272@linux.intel.com> <20200922053515.GA97687@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200922053515.GA97687@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 08:35:15AM +0300, Jarkko Sakkinen wrote: > On Tue, Sep 22, 2020 at 08:30:06AM +0300, Jarkko Sakkinen wrote: > > On Mon, Sep 21, 2020 at 02:18:49PM -0700, Sean Christopherson wrote: > > > 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. > > > > Right, the VM_MAYEXEC in the code is nested under VM_EXEC check. > > > > I'm only wondering why not block noexec completely with any permissions, > > i.e. why not just have unconditional VM_MAYEXEC check? > > I.e. why not this: > > static int __sgx_encl_add_page(struct sgx_encl *encl, > struct sgx_encl_page *encl_page, > struct sgx_epc_page *epc_page, > struct sgx_secinfo *secinfo, unsigned long src) > { > struct sgx_pageinfo pginfo; > struct vm_area_struct *vma; > struct page *src_page; > int ret; > > vma = find_vma(current->mm, src); > if (!vma) > return -EFAULT; > > if (!(vma->vm_flags & VM_MAYEXEC)) > return -EACCES; > > I'm not seeing the reason for "partial support" for noexec partitions. > > If there is a good reason, fine, let's just then document it. There are scenarios I can contrive, e.g. loading an enclave from a noexec filesystem without having to copy the entire enclave to anon memory, or loading a data payload from a noexec FS. They're definitely contrived scenarios, but given that we also want the ->mprotect() hook/behavior for potential LSM interaction, supporting said contrived scenarios costs is "free".