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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 E30E1C3A59F for ; Thu, 29 Aug 2019 16:00:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BD87A205ED for ; Thu, 29 Aug 2019 16:00:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727899AbfH2QAC (ORCPT ); Thu, 29 Aug 2019 12:00:02 -0400 Received: from mga01.intel.com ([192.55.52.88]:55220 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727600AbfH2QAC (ORCPT ); Thu, 29 Aug 2019 12:00:02 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Aug 2019 09:00:01 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,443,1559545200"; d="scan'208";a="205778004" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.41]) by fmsmga004.fm.intel.com with ESMTP; 29 Aug 2019 09:00:01 -0700 Date: Thu, 29 Aug 2019 09:00:01 -0700 From: Sean Christopherson To: Jarkko Sakkinen Cc: linux-sgx@vger.kernel.org Subject: Re: [PATCH v2 2/5] x86/sgx: Reject concurrent ioctls on single enclave Message-ID: <20190829160001.GD26580@linux.intel.com> References: <20190827192717.27312-1-sean.j.christopherson@intel.com> <20190827192717.27312-3-sean.j.christopherson@intel.com> <20190829131543.ejdsviysr2u33rnj@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190829131543.ejdsviysr2u33rnj@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 Thu, Aug 29, 2019 at 04:15:43PM +0300, Jarkko Sakkinen wrote: > On Tue, Aug 27, 2019 at 12:27:14PM -0700, Sean Christopherson wrote: > > Except for ENCLAVE_SET_ATTRIBUTE, all SGX ioctls() must be executed > > serially to successfully initialize an enclave, e.g. the kernel already > > strictly requires ECREATE->EADD->EINIT, and concurrent EADDs will result > > in an unstable MRENCLAVE. Explicitly enforce serialization by returning > > EINVAL if userspace attempts an ioctl while a different ioctl for the > > same enclave is in progress. > > > > The primary beneficiary of explicit serialization is sgx_encl_grow() as > > it no longer has to deal with dropping and reacquiring encl->lock when > > a new VA page needs to be allocated. Eliminating the lock juggling in > > sgx_encl_grow() paves the way for fixing a lock ordering bug in > > ENCLAVE_ADD_PAGE without having to also juggle mm->mmap_sem. > > > > Serializing ioctls also fixes a race between ENCLAVE_CREATE and > > ENCLAVE_SET_ATTRIBUTE, as the latter does not take encl->lock, e.g. > > concurrent updates to allowed_attributes could result in a stale > > value. The race could also be fixed by taking encl->lock or making > > allowed_attributes atomic, but both add unnecessary overhead with this > > change applied. > > > > Signed-off-by: Sean Christopherson > > #PF handler should be good as it has this conditional: > > flags = atomic_read(&encl->flags); > > if ((flags & SGX_ENCL_DEAD) || !(flags & SGX_ENCL_INITIALIZED)) > return ERR_PTR(-EFAULT); > > What about the reclaimer? Can you elaborate? I'm not sure what you're asking.