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=-2.3 required=3.0 tests=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 AC501C3A59F for ; Thu, 29 Aug 2019 18:43:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 82F55215EA for ; Thu, 29 Aug 2019 18:43:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727867AbfH2Sne (ORCPT ); Thu, 29 Aug 2019 14:43:34 -0400 Received: from mga14.intel.com ([192.55.52.115]:10560 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727779AbfH2Sne (ORCPT ); Thu, 29 Aug 2019 14:43:34 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Aug 2019 11:43:33 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,444,1559545200"; d="scan'208";a="193060622" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.41]) by orsmga002.jf.intel.com with ESMTP; 29 Aug 2019 11:43:33 -0700 Date: Thu, 29 Aug 2019 11:43:33 -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: <20190829184332.GA27262@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> <20190829160001.GD26580@linux.intel.com> <20190829181438.oxix5d7qfgru7bd7@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190829181438.oxix5d7qfgru7bd7@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 09:14:38PM +0300, Jarkko Sakkinen wrote: > On Thu, Aug 29, 2019 at 09:00:01AM -0700, Sean Christopherson wrote: > > > #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. > > I'm thinking of a race between list_add() in the ioctl and > list_move_tail() in the reclaimer. Ah crud, I forgot that the reclaimer can manipulate the list of VA pages, I was thinking they were invisible to the reclaimer. > A quick way to fix this would be move sgx_alloc_va_page() from > sgx_encl_grow() and return NULL if a new allocation is required. We don't even need to do that, moving the list_add() from sgx_encl_grow() to its caller would be sufficient. Same concept, but the allocation would be handled by sgx_encl_grow() instead of having to duplicate that code in sgx_encl_add_page() and sgx_encl_create(). > In the ioctl you can then allocate the page before taking locks and > do "list_add(&va_page->list, &encl->va_pages);" behind the locks.