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 76B3FC2B9F2 for ; Sat, 22 May 2021 23:39:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4C9F661163 for ; Sat, 22 May 2021 23:39:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231452AbhEVXk7 (ORCPT ); Sat, 22 May 2021 19:40:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:58648 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231433AbhEVXk7 (ORCPT ); Sat, 22 May 2021 19:40:59 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id C8A6461168 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=1621726772; bh=zDjcQM82T3zWBFosGa25gfnhyhFFiGZ7lvxtB2YXTlI=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=dIR37umbmtqruno2pZLXckneeQzZDJCTOUKhFvNThmHs4dIavCTt4fEwhvhTCwqXM 2G0CvCmld4RQED0h40x296yxHB+i8mzTiVyz/g41KFfWS5M+BX81sNwOFpFSJURceV zfUPGPPPaqDbsNKqWCwLQ2OJlYVTodNEEbOOFunCEHpQGCF+e8nvA9PK33j59Z3rWO ylrQ41f8bz4LOUi3XhVCAT6XvIw2TSzcq4w+XK5Ldlb1QQB+9/ZJ2pFugEkVdTgA95 frLXRmA3lH55BlNTRsD2uiLQIZF6JLRRuzlaMeUaqvPv0PSPS6iWKrfUX7h046Q1kG UFeRDTPFc220g== Received: by mail-ej1-f49.google.com with SMTP id et19so28961755ejc.4 for ; Sat, 22 May 2021 16:39:32 -0700 (PDT) X-Gm-Message-State: AOAM531ARpdhiTpJdzYfkmqOBYRvU0E033nQnOa0RvNIB3dnCGu23m3/ s/tSDdhcdtaBVCS3dFwtqrQWsiIDXpT1SvQOZ2eDBA== 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-arch@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