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_HELO_NONE,SPF_PASS 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 AA53CC3A5A1 for ; Thu, 22 Aug 2019 16:31:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 855FF233FE for ; Thu, 22 Aug 2019 16:31:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732721AbfHVQbm (ORCPT ); Thu, 22 Aug 2019 12:31:42 -0400 Received: from mga11.intel.com ([192.55.52.93]:8135 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731880AbfHVQbm (ORCPT ); Thu, 22 Aug 2019 12:31:42 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 22 Aug 2019 09:31:41 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,417,1559545200"; d="scan'208";a="196283605" Received: from greathea-mobl2.ger.corp.intel.com ([10.252.39.37]) by fmsmga001.fm.intel.com with ESMTP; 22 Aug 2019 09:31:40 -0700 Message-ID: Subject: Re: [PATCH 4/5] x86/sgx: Validate TCS permssions in sgx_validate_secinfo() From: Jarkko Sakkinen To: Sean Christopherson Cc: linux-sgx@vger.kernel.org Date: Thu, 22 Aug 2019 19:31:39 +0300 In-Reply-To: <20190822035510.GV29345@linux.intel.com> References: <20190819152544.7296-1-jarkko.sakkinen@linux.intel.com> <20190819152544.7296-5-jarkko.sakkinen@linux.intel.com> <20190822035510.GV29345@linux.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.32.2-1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-sgx-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Wed, 2019-08-21 at 20:55 -0700, Sean Christopherson wrote: > Why are we validating the TCS protection bits? Hardware ignores them, so > why do we care? sgx_ioc_enclave_add_page() sets the internal protection > bits so there's no danger of putting the wrong thing in the page tables. I think that in this commit I got it wrong but I think this is awkward: /* * TCS pages must always RW set for CPU access while the SECINFO * permissions are *always* zero - the CPU ignores the user provided * values and silently overwrites with zero permissions. */ if ((secinfo.flags & SGX_SECINFO_PAGE_TYPE_MASK) == SGX_SECINFO_TCS) prot |= PROT_READ | PROT_WRITE; In my opinion the right thing to do would be check that SECINFO has *at minimum* RW and return -EINVAL if not. I don't like the SGX silently adjusting permissions like this. /Jarkko