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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 A46E4C3A5A3 for ; Tue, 27 Aug 2019 16:42:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7745D21881 for ; Tue, 27 Aug 2019 16:42:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728061AbfH0QmF (ORCPT ); Tue, 27 Aug 2019 12:42:05 -0400 Received: from mga07.intel.com ([134.134.136.100]:32161 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727401AbfH0QmF (ORCPT ); Tue, 27 Aug 2019 12:42:05 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Aug 2019 09:42:04 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,437,1559545200"; d="scan'208";a="185346811" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.41]) by orsmga006.jf.intel.com with ESMTP; 27 Aug 2019 09:42:04 -0700 Date: Tue, 27 Aug 2019 09:42:04 -0700 From: Sean Christopherson To: Jarkko Sakkinen Cc: linux-sgx@vger.kernel.org Subject: Re: [PATCH 1/4] x86/sgx: Ensure enclave state is visible before marking it created Message-ID: <20190827164204.GF27459@linux.intel.com> References: <20190827001128.25066-1-sean.j.christopherson@intel.com> <20190827001128.25066-2-sean.j.christopherson@intel.com> <20190827112044.rduraacnr242rpxj@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190827112044.rduraacnr242rpxj@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-sgx-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Tue, Aug 27, 2019 at 02:20:44PM +0300, Jarkko Sakkinen wrote: > On Mon, Aug 26, 2019 at 05:11:25PM -0700, Sean Christopherson wrote: > > Add a memory barrier pair to ensure all enclave state is visible in > > memory prior to SGX_ENCL_CREATED being set. Without the barries, adding > > pages and/or initializing the enclaves could theoretically consume stale > > data. > > > > Signed-off-by: Sean Christopherson > > --- > > arch/x86/kernel/cpu/sgx/ioctl.c | 16 +++++++++++++--- > > 1 file changed, 13 insertions(+), 3 deletions(-) > > > > diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c > > index 911ff3b0f061..7134d68aecb3 100644 > > --- a/arch/x86/kernel/cpu/sgx/ioctl.c > > +++ b/arch/x86/kernel/cpu/sgx/ioctl.c > > @@ -163,6 +163,15 @@ static struct sgx_encl_page *sgx_encl_page_alloc(struct sgx_encl *encl, > > return encl_page; > > } > > > > +static bool is_encl_created(struct sgx_encl *encl) > > +{ > > + bool created = encl->flags & SGX_ENCL_CREATED; > > + > > + /* Pairs with smp_wmb() in sgx_encl_create(). */ > > + smp_rmb(); > > + return created; > > +} > > what if you just convert the flags to atomic_t? That would fix this > issue and would prevent analogous issues from occuring. I thought about that too, but originally discarded the idea because I was worried doing so would negatively impact the other uses of flags. After actually implementing the change, I think the positives outweigh the negatives, so I'll send a v2 with this suggestion.