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=-11.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 43026C4707F for ; Sat, 22 May 2021 23:39:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 206B161076 for ; Sat, 22 May 2021 23:39:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231474AbhEVXlA (ORCPT ); Sat, 22 May 2021 19:41:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:58706 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231440AbhEVXk7 (ORCPT ); Sat, 22 May 2021 19:40:59 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id EB873611AB for ; Sat, 22 May 2021 23:39:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1621726773; bh=zDjcQM82T3zWBFosGa25gfnhyhFFiGZ7lvxtB2YXTlI=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=B+TwDyrWGdAjEvCjjmZ1r2ApPYlRVCsMUQTzIrMnFG9NNW22o0HCcvbabvN9ZmwzI hJpNC7YT1zc+wJP7BEcfl9DpfT9sWrDhD9IMV/uqVnhfK6UtolN4p/KsH8UnLRzf4R 8UrPti9HeYVeCFyXy8R7zrdLHuLp+1QNyKhU5fAtnD2Hy3trJIrxMSVkrTmofmZvFw cDdaLbPINEZ9qn0UQ0JyIphclHsqWkFK1v1KEoofR82jPoEvUA1G2HTg7xclExac6s xO+nceMPqnnXVXFFJYS7NI/qVyDOZ2kLadnfxKyM+bjxSVw7pqeX0axB4/wveF1Wnm DEnmPwPWrL3Tg== Received: by mail-ej1-f41.google.com with SMTP id l1so35999481ejb.6 for ; Sat, 22 May 2021 16:39:32 -0700 (PDT) X-Gm-Message-State: AOAM532x81YphxNknd9Q/CRB5ZOQe+BBMIe7xS8R2XXHJ4TA82GDfL70 7ANfcdOpB6FSZCUcn5KYihwauXMTBQuYnq5H2Tvw5w== X-Google-Smtp-Source: ABdhPJwAVu0oyGtUpR1c3WqPW+v7885e6HHBhZnVMCDtrkGrfBYPAbfHVT6rxsNYk/ProlHmSNOEIVRIb18Me5LG1jA= X-Received: by 2002:a17:906:458:: with SMTP id e24mr17084955eja.199.1621726771411; Sat, 22 May 2021 16:39:31 -0700 (PDT) MIME-Version: 1.0 References: <20210521221211.29077-1-yu-cheng.yu@intel.com> <20210521221211.29077-25-yu-cheng.yu@intel.com> In-Reply-To: <20210521221211.29077-25-yu-cheng.yu@intel.com> From: Andy Lutomirski Date: Sat, 22 May 2021 16:39:19 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v27 24/31] x86/cet/shstk: Handle thread shadow stack To: Yu-cheng Yu Cc: X86 ML , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , LKML , "open list:DOCUMENTATION" , Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , 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 Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 21, 2021 at 3:14 PM Yu-cheng Yu wrote: > diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c > index 5ea2b494e9f9..8e5f772181b9 100644 > --- a/arch/x86/kernel/shstk.c > +++ b/arch/x86/kernel/shstk.c > @@ -71,6 +71,53 @@ int shstk_setup(void) > return 0; > } > > +int shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long clone_flags, > + unsigned long stack_size) > +{ ... > + state = get_xsave_addr(&tsk->thread.fpu.state.xsave, XFEATURE_CET_USER); > + if (!state) > + return -EINVAL; > + The get_xsave_addr() API is horrible, and we already have one egregiously buggy instance in the kernel. Let's not add another dubious use case. If state == NULL, this means that CET_USER is in its init state. CET_USER in the init state should behave identically regardless of whether XINUSE[CET_USER] is set. Can you please adjust this code accordingly? Thanks, Andy 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=-11.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 43A41C4707E for ; Sat, 22 May 2021 23:39:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D12DB61168 for ; Sat, 22 May 2021 23:39:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D12DB61168 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3191B6B0096; Sat, 22 May 2021 19:39:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2A1A36B0098; Sat, 22 May 2021 19:39:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0F5926B0099; Sat, 22 May 2021 19:39:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0112.hostedemail.com [216.40.44.112]) by kanga.kvack.org (Postfix) with ESMTP id CF3F36B0096 for ; Sat, 22 May 2021 19:39:34 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 67144180ACF9A for ; Sat, 22 May 2021 23:39:34 +0000 (UTC) X-FDA: 78170486268.10.88F0EDD Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf29.hostedemail.com (Postfix) with ESMTP id C10162C0 for ; Sat, 22 May 2021 23:39:28 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 079E661241 for ; Sat, 22 May 2021 23:39:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1621726773; bh=zDjcQM82T3zWBFosGa25gfnhyhFFiGZ7lvxtB2YXTlI=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=B+TwDyrWGdAjEvCjjmZ1r2ApPYlRVCsMUQTzIrMnFG9NNW22o0HCcvbabvN9ZmwzI hJpNC7YT1zc+wJP7BEcfl9DpfT9sWrDhD9IMV/uqVnhfK6UtolN4p/KsH8UnLRzf4R 8UrPti9HeYVeCFyXy8R7zrdLHuLp+1QNyKhU5fAtnD2Hy3trJIrxMSVkrTmofmZvFw cDdaLbPINEZ9qn0UQ0JyIphclHsqWkFK1v1KEoofR82jPoEvUA1G2HTg7xclExac6s xO+nceMPqnnXVXFFJYS7NI/qVyDOZ2kLadnfxKyM+bjxSVw7pqeX0axB4/wveF1Wnm DEnmPwPWrL3Tg== Received: by mail-ej1-f43.google.com with SMTP id f18so5834434ejq.10 for ; Sat, 22 May 2021 16:39:32 -0700 (PDT) X-Gm-Message-State: AOAM531MUb4cHmz6Hu2V5Lri30IsYGsp8gpibXQtkQGo21SDfkA5s8bn YU0U7NQGirq1Qrb/poLseKa4cx825VuGCJ03rqnBkg== X-Google-Smtp-Source: ABdhPJwAVu0oyGtUpR1c3WqPW+v7885e6HHBhZnVMCDtrkGrfBYPAbfHVT6rxsNYk/ProlHmSNOEIVRIb18Me5LG1jA= X-Received: by 2002:a17:906:458:: with SMTP id e24mr17084955eja.199.1621726771411; Sat, 22 May 2021 16:39:31 -0700 (PDT) MIME-Version: 1.0 References: <20210521221211.29077-1-yu-cheng.yu@intel.com> <20210521221211.29077-25-yu-cheng.yu@intel.com> In-Reply-To: <20210521221211.29077-25-yu-cheng.yu@intel.com> From: Andy Lutomirski Date: Sat, 22 May 2021 16:39:19 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v27 24/31] x86/cet/shstk: Handle thread shadow stack To: Yu-cheng Yu Cc: X86 ML , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , LKML , "open list:DOCUMENTATION" , Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , 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 Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=B+TwDyrW; spf=pass (imf29.hostedemail.com: domain of luto@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=luto@kernel.org; dmarc=pass (policy=none) header.from=kernel.org X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: C10162C0 X-Stat-Signature: wcqb5m96gwqw5436gabe3cehigdzgwij X-HE-Tag: 1621726768-866409 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, May 21, 2021 at 3:14 PM Yu-cheng Yu wrote: > diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c > index 5ea2b494e9f9..8e5f772181b9 100644 > --- a/arch/x86/kernel/shstk.c > +++ b/arch/x86/kernel/shstk.c > @@ -71,6 +71,53 @@ int shstk_setup(void) > return 0; > } > > +int shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long clone_flags, > + unsigned long stack_size) > +{ ... > + state = get_xsave_addr(&tsk->thread.fpu.state.xsave, XFEATURE_CET_USER); > + if (!state) > + return -EINVAL; > + The get_xsave_addr() API is horrible, and we already have one egregiously buggy instance in the kernel. Let's not add another dubious use case. If state == NULL, this means that CET_USER is in its init state. CET_USER in the init state should behave identically regardless of whether XINUSE[CET_USER] is set. Can you please adjust this code accordingly? Thanks, Andy