From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yu-cheng Yu Subject: Re: [RFC PATCH v3 05/24] Documentation/x86: Add CET description Date: Thu, 30 Aug 2018 15:49:51 -0700 Message-ID: <1535669391.28781.7.camel@intel.com> References: <20180830143904.3168-1-yu-cheng.yu@intel.com> <20180830143904.3168-6-yu-cheng.yu@intel.com> <20180830203948.GB1936@amd> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20180830203948.GB1936@amd> Sender: linux-kernel-owner@vger.kernel.org To: Pavel Machek 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 , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Peter Zijlstra List-Id: linux-arch.vger.kernel.org On Thu, 2018-08-30 at 22:39 +0200, Pavel Machek wrote: > Hi! > > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt > > b/Documentation/admin-guide/kernel-parameters.txt > > index 9871e649ffef..b090787188b4 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -2764,6 +2764,12 @@ > >   noexec=on: enable non-executable mappings > > (default) > >   noexec=off: disable non-executable > > mappings > >   > > + no_cet_ibt [X86-64] Disable indirect branch > > tracking for user-mode > > + applications > > + > > + no_cet_shstk [X86-64] Disable shadow stack support > > for user-mode > > + applications > Hmm, not too consistent with "nosmap" below. Would it make sense to > have cet=on/off/ibt/shstk instead? > > > > > +++ b/Documentation/x86/intel_cet.rst > > @@ -0,0 +1,252 @@ > > +========================================= > > +Control Flow Enforcement Technology (CET) > > +========================================= > > + > > +[1] Overview > > +============ > > + > > +Control Flow Enforcement Technology (CET) provides protection > > against > > +return/jump-oriented programing (ROP) attacks. > Can you add something like "It attempts to protect process from > running arbitrary code even after attacker has control of its stack" > -- for people that don't know what ROP is, and perhaps link to > wikipedia explaining ROP or something... > > > > > It can be implemented > > +to protect both the kernel and applications.  In the first phase, > > +only the user-mode protection is implemented for the 64-bit > > kernel. > > +Thirty-two bit applications are supported under the compatibility > 32-bit (for consistency). > > Ok, so CET stops execution of malicious code before architectural > effects are visible, correct? Does it prevent micro-architectural > effects of the malicious code? (cache content would be one example; > see Spectre). > > > > > +[3] Application Enabling > > +======================== > "Enabling CET in applications" ? > > > > > +Signal > > +------ > > + > > +The main program and its signal handlers use the same > > SHSTK.  Because > > +the SHSTK stores only return addresses, we can estimate a large > > +enough SHSTK to cover the condition that both the program stack > > and > > +the sigaltstack run out. > English? Is it estimate or is it large enough? "a large" -- "a" > should > be deleted AFAICT. >   I will work on these, thanks! From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga17.intel.com ([192.55.52.151]:52478 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725836AbeHaC6l (ORCPT ); Thu, 30 Aug 2018 22:58:41 -0400 Message-ID: <1535669391.28781.7.camel@intel.com> Subject: Re: [RFC PATCH v3 05/24] Documentation/x86: Add CET description From: Yu-cheng Yu Date: Thu, 30 Aug 2018 15:49:51 -0700 In-Reply-To: <20180830203948.GB1936@amd> References: <20180830143904.3168-1-yu-cheng.yu@intel.com> <20180830143904.3168-6-yu-cheng.yu@intel.com> <20180830203948.GB1936@amd> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Pavel Machek 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 , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Peter Zijlstra , "Ravi V. Shankar" , Vedvyas Shanbhogue Message-ID: <20180830224951.l7mIFNTrUX_qqJ8OScCR0zAb5yJeUfe9Z5jEQqMIwPo@z> On Thu, 2018-08-30 at 22:39 +0200, Pavel Machek wrote: > Hi! > > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt > > b/Documentation/admin-guide/kernel-parameters.txt > > index 9871e649ffef..b090787188b4 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -2764,6 +2764,12 @@ > >   noexec=on: enable non-executable mappings > > (default) > >   noexec=off: disable non-executable > > mappings > >   > > + no_cet_ibt [X86-64] Disable indirect branch > > tracking for user-mode > > + applications > > + > > + no_cet_shstk [X86-64] Disable shadow stack support > > for user-mode > > + applications > Hmm, not too consistent with "nosmap" below. Would it make sense to > have cet=on/off/ibt/shstk instead? > > > > > +++ b/Documentation/x86/intel_cet.rst > > @@ -0,0 +1,252 @@ > > +========================================= > > +Control Flow Enforcement Technology (CET) > > +========================================= > > + > > +[1] Overview > > +============ > > + > > +Control Flow Enforcement Technology (CET) provides protection > > against > > +return/jump-oriented programing (ROP) attacks. > Can you add something like "It attempts to protect process from > running arbitrary code even after attacker has control of its stack" > -- for people that don't know what ROP is, and perhaps link to > wikipedia explaining ROP or something... > > > > > It can be implemented > > +to protect both the kernel and applications.  In the first phase, > > +only the user-mode protection is implemented for the 64-bit > > kernel. > > +Thirty-two bit applications are supported under the compatibility > 32-bit (for consistency). > > Ok, so CET stops execution of malicious code before architectural > effects are visible, correct? Does it prevent micro-architectural > effects of the malicious code? (cache content would be one example; > see Spectre). > > > > > +[3] Application Enabling > > +======================== > "Enabling CET in applications" ? > > > > > +Signal > > +------ > > + > > +The main program and its signal handlers use the same > > SHSTK.  Because > > +the SHSTK stores only return addresses, we can estimate a large > > +enough SHSTK to cover the condition that both the program stack > > and > > +the sigaltstack run out. > English? Is it estimate or is it large enough? "a large" -- "a" > should > be deleted AFAICT. >   I will work on these, thanks!