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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 6CC49C43462 for ; Tue, 11 May 2021 18:35:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4596D61919 for ; Tue, 11 May 2021 18:35:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232080AbhEKSgT (ORCPT ); Tue, 11 May 2021 14:36:19 -0400 Received: from mga06.intel.com ([134.134.136.31]:42688 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231858AbhEKSgS (ORCPT ); Tue, 11 May 2021 14:36:18 -0400 IronPort-SDR: VLN+z1pa7BfBiZJFHMOFrVeCfEv5JbOkgdQlsnnA1nGJAlBdL1oVdqZxfGjUtF8HgYMk4kM4vn lQB5w4qYtIhA== X-IronPort-AV: E=McAfee;i="6200,9189,9981"; a="260779848" X-IronPort-AV: E=Sophos;i="5.82,291,1613462400"; d="scan'208";a="260779848" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 May 2021 11:35:06 -0700 IronPort-SDR: 2KWMocZbxX5tyqZAg7OsM0mkEVoJfqigNIZiG7v7OmxmAmJ4UREKqpCUEnT+ESKdjh0nogGOde b12AZro4a4Mg== X-IronPort-AV: E=Sophos;i="5.82,291,1613462400"; d="scan'208";a="537136995" Received: from yyu32-mobl1.amr.corp.intel.com (HELO [10.212.34.147]) ([10.212.34.147]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 May 2021 11:35:04 -0700 Subject: Re: [PATCH v26 23/30] x86/cet/shstk: Handle thread shadow stack To: Borislav Petkov Cc: x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu , Haitao Huang References: <20210427204315.24153-1-yu-cheng.yu@intel.com> <20210427204315.24153-24-yu-cheng.yu@intel.com> From: "Yu, Yu-cheng" Message-ID: Date: Tue, 11 May 2021 11:35:03 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/10/2021 7:15 AM, Borislav Petkov wrote: > On Tue, Apr 27, 2021 at 01:43:08PM -0700, Yu-cheng Yu wrote: >> @@ -181,6 +184,12 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg, >> if (clone_flags & CLONE_SETTLS) >> ret = set_new_tls(p, tls); >> >> +#ifdef CONFIG_X86_64 > > IS_ENABLED > >> + /* Allocate a new shadow stack for pthread */ >> + if (!ret) >> + ret = shstk_setup_thread(p, clone_flags, stack_size); >> +#endif >> + > > And why is this addition here... > >> if (!ret && unlikely(test_tsk_thread_flag(current, TIF_IO_BITMAP))) >> io_bitmap_share(p); > > ... instead of here? > > <--- > io_bitmap_share() does refcount_inc(¤t->thread.io_bitmap->refcnt), and the function won't fail. However, shadow stack allocation can fail. So, maybe leave io_bitmap_share() at the end? Thanks, Yu-cheng