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 83F7CC43387 for ; Mon, 17 Dec 2018 18:49:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5861F20874 for ; Mon, 17 Dec 2018 18:49:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389211AbeLQStA (ORCPT ); Mon, 17 Dec 2018 13:49:00 -0500 Received: from mga04.intel.com ([192.55.52.120]:16971 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726628AbeLQSs7 (ORCPT ); Mon, 17 Dec 2018 13:48:59 -0500 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 fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 17 Dec 2018 10:48:58 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,366,1539673200"; d="scan'208";a="119045611" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.154]) by orsmga002.jf.intel.com with ESMTP; 17 Dec 2018 10:48:58 -0800 Date: Mon, 17 Dec 2018 10:48:58 -0800 From: Sean Christopherson To: Jarkko Sakkinen 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: <20181217184858.GF12491@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> <20181217184333.GA26920@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181217184333.GA26920@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) 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 08:43:33PM +0200, Jarkko Sakkinen wrote: > 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. We can't set mm to NULL as we need it to unregister the notifier, and I'm fairly certain attempting to unregister in the release callback will deadlock.