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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 837EFC43387 for ; Mon, 17 Dec 2018 18:43:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5DC43214D8 for ; Mon, 17 Dec 2018 18:43:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389146AbeLQSno (ORCPT ); Mon, 17 Dec 2018 13:43:44 -0500 Received: from mga01.intel.com ([192.55.52.88]:37701 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726653AbeLQSnl (ORCPT ); Mon, 17 Dec 2018 13:43:41 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 17 Dec 2018 10:43:40 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,366,1539673200"; d="scan'208";a="304554684" Received: from quwen-mobl.ccr.corp.intel.com (HELO localhost) ([10.249.254.215]) by fmsmga005.fm.intel.com with ESMTP; 17 Dec 2018 10:43:34 -0800 Date: Mon, 17 Dec 2018 20:43:33 +0200 From: Jarkko Sakkinen To: Sean Christopherson Cc: Dave Hansen , x86@kernel.org, platform-driver-x86@vger.kernel.org, linux-sgx@vger.kernel.org, nhorman@redhat.com, npmccallum@redhat.com, serge.ayoun@intel.com, shay.katz-zamir@intel.com, haitao.huang@linux.intel.com, andriy.shevchenko@linux.intel.com, tglx@linutronix.de, kai.svahn@intel.com, mark.shanahan@intel.com, luto@amacapital.net, Suresh Siddha , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Darren Hart , Andy Shevchenko , "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" Subject: Re: [PATCH v17 18/23] platform/x86: Intel SGX driver Message-ID: <20181217184333.GA26920@linux.intel.com> References: <20181116010412.23967-1-jarkko.sakkinen@linux.intel.com> <20181116010412.23967-19-jarkko.sakkinen@linux.intel.com> <7d5cde02-4649-546b-0f03-2d6414bb80b5@intel.com> <20181217180102.GA12560@linux.intel.com> <20181217183613.GD12491@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181217183613.GD12491@linux.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 17, 2018 at 10:36:13AM -0800, Sean Christopherson wrote: > I'm pretty sure doing mmget() would result in circular dependencies and > a zombie enclave. In the do_exit() case where a task is abruptly killed: > > - __mmput() is never called because the enclave holds a ref > - sgx_encl_release() is never be called because its VMAs hold refs > - sgx_vma_close() is never called because __mmput()->exit_mmap() is > blocked and the process itself is dead, i.e. won't unmap anything. Right, it does, you are absolutely right. Tried it and removed the commit already. Well, what we came up from your suggestion i.e. setting mm to NULL and checking that is very subtle change and does not have any such circular dependencies. We'll go with that. /Jarkko