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=-8.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_MED,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 7C63BC433F4 for ; Thu, 30 Aug 2018 18:00:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2963220838 for ; Thu, 30 Aug 2018 18:00:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ao7IWi+P" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2963220838 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727572AbeH3WDS (ORCPT ); Thu, 30 Aug 2018 18:03:18 -0400 Received: from mail-oi0-f66.google.com ([209.85.218.66]:45475 "EHLO mail-oi0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726674AbeH3WDS (ORCPT ); Thu, 30 Aug 2018 18:03:18 -0400 Received: by mail-oi0-f66.google.com with SMTP id t68-v6so16976927oie.12 for ; Thu, 30 Aug 2018 10:59:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=AhFK2aFvWPveEyK+LlBfYW09h2A3k7IjDUBtR3SoN2g=; b=ao7IWi+PXEG69rKSDk02ftHLPTMga2Vc+XT3LXRfWiVePaNLFrsj1FXPx0s10r7h3X UpLhIpVnO15PqNtFAF40nR4dJCS/CtAqlwntUMHt5SKOw31NTLRVvgpkOldbKtkmKi1h LZDlmt4H+jChfE7tPPgaRM2WWogOBy8VCF4uSlRXcsI8QuH1i0XnX53ShpPNZX3X46Pu 0OLtiQUqOVrkslPZSbbPwv0gkwIaGcZucPyQeTu21uqoy17Zobrzk4gb0bSJNI/pOGCo 5LCy9dTDnLV7jOojJYLkAVfEwoxHrgHGYO1I8bBw3DwIJ8z+JfSGt1JWAfTOyPIsoj1Q 1M1g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=AhFK2aFvWPveEyK+LlBfYW09h2A3k7IjDUBtR3SoN2g=; b=oDv1lxNqunLCQX6aq3E8XqebQGmwbsVcy4cTxxJZUGEXBK/2O8zNFdPincsx24OXj0 txIhKSUXfNlZffa5iDyYJo5HfVd2L0//BsLKOTqe8+kxtPfgVmKojmSwkUVvzEtf5Q6J +7GVP+bO4NAv/MOzPWboV8J2AApc9dZzxwIszAZsz5wgBXXWFCOBA6oCu2NYr43fpM/Z S4av4s8UYfjDbs5Q23TmFUS3K98mJxBy06C8h6dG0DVkTzdnyKD8JULwi4Sj33Zjzt3w 0Nd/BEYVbKY9ZPOMpTPlvNKaPG3koxea7l3jegdYH04G1+t+vnn9L6KP4VheTiFZgB3j xJkw== X-Gm-Message-State: APzg51D8NKyo3Gbbrc1p8M+vKnKnqOm28EbyzSlN48I+QL12CWmy4C27 wQRCbVTENg2NGAv4GiuM3l4si5s+8TKXnV50CVxmqQ== X-Google-Smtp-Source: ANB0VdauerD2wyrOZxhWfskp0HKKdOE+1QXxPjRftG0xBuYfx8D4lGSd3ijm3jHVUuMIpYuvUe+s2iUJaaTrhCuskZ8= X-Received: by 2002:aca:b40a:: with SMTP id d10-v6mr3866636oif.190.1535651999272; Thu, 30 Aug 2018 10:59:59 -0700 (PDT) MIME-Version: 1.0 References: <20180830143904.3168-1-yu-cheng.yu@intel.com> <20180830143904.3168-13-yu-cheng.yu@intel.com> <079a55f2-4654-4adf-a6ef-6e480b594a2f@linux.intel.com> <1535649960.26689.15.camel@intel.com> <33d45a12-513c-eba2-a2de-3d6b630e928e@linux.intel.com> <1535651666.27823.6.camel@intel.com> In-Reply-To: <1535651666.27823.6.camel@intel.com> From: Jann Horn Date: Thu, 30 Aug 2018 19:59:32 +0200 Message-ID: Subject: Re: [RFC PATCH v3 12/24] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW To: yu-cheng.yu@intel.com Cc: Dave Hansen , "the arch/x86 maintainers" , "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , kernel list , linux-doc@vger.kernel.org, Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Florian Weimer , hjl.tools@gmail.com, Jonathan Corbet , keescook@chromiun.org, Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , ravi.v.shankar@intel.com, vedvyas.shanbhogue@intel.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 30, 2018 at 7:58 PM Yu-cheng Yu wrote: > > On Thu, 2018-08-30 at 10:33 -0700, Dave Hansen wrote: > > On 08/30/2018 10:26 AM, Yu-cheng Yu wrote: > > > > > > We don't have the guard page now, but there is a shadow stack > > > token > > > there, which cannot be used as a return address. > > The overall concern is that we could overflow into a page that we > > did > > not intend. Either another actual shadow stack or something that a > > page > > that the attacker constructed, like the transient scenario Jann > > described. > > > > A task could go beyond the bottom of its shadow stack by doing either > 'ret' or 'incssp'. If it is the 'ret' case, the token prevents it. > If it is the 'incssp' case, a guard page cannot prevent it entirely, > right? I mean the other direction, on "call". From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jann Horn Subject: Re: [RFC PATCH v3 12/24] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW Date: Thu, 30 Aug 2018 19:59:32 +0200 Message-ID: References: <20180830143904.3168-1-yu-cheng.yu@intel.com> <20180830143904.3168-13-yu-cheng.yu@intel.com> <079a55f2-4654-4adf-a6ef-6e480b594a2f@linux.intel.com> <1535649960.26689.15.camel@intel.com> <33d45a12-513c-eba2-a2de-3d6b630e928e@linux.intel.com> <1535651666.27823.6.camel@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <1535651666.27823.6.camel@intel.com> Sender: linux-kernel-owner@vger.kernel.org To: yu-cheng.yu@intel.com Cc: Dave Hansen , the arch/x86 maintainers , "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , kernel list , linux-doc@vger.kernel.org, Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Florian Weimer , hjl.tools@gmail.com, Jonathan Corbet , keescook@chromiun.org, Mike Kravetz , Nadav Amit , Oleg Nesterov Pavel Machek List-Id: linux-api@vger.kernel.org On Thu, Aug 30, 2018 at 7:58 PM Yu-cheng Yu wrote: > > On Thu, 2018-08-30 at 10:33 -0700, Dave Hansen wrote: > > On 08/30/2018 10:26 AM, Yu-cheng Yu wrote: > > > > > > We don't have the guard page now, but there is a shadow stack > > > token > > > there, which cannot be used as a return address. > > The overall concern is that we could overflow into a page that we > > did > > not intend. Either another actual shadow stack or something that a > > page > > that the attacker constructed, like the transient scenario Jann > > described. > > > > A task could go beyond the bottom of its shadow stack by doing either > 'ret' or 'incssp'. If it is the 'ret' case, the token prevents it. > If it is the 'incssp' case, a guard page cannot prevent it entirely, > right? I mean the other direction, on "call".