From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751815AbdFIQLD (ORCPT ); Fri, 9 Jun 2017 12:11:03 -0400 Received: from mx2.suse.de ([195.135.220.15]:40207 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751527AbdFIQLA (ORCPT ); Fri, 9 Jun 2017 12:11:00 -0400 Date: Fri, 9 Jun 2017 18:10:31 +0200 From: Borislav Petkov To: Ricardo Neri Cc: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Andrew Morton , Brian Gerst , Chris Metcalf , Dave Hansen , Paolo Bonzini , Masami Hiramatsu , Huang Rui , Jiri Slaby , Jonathan Corbet , "Michael S. Tsirkin" , Paul Gortmaker , Vlastimil Babka , Chen Yucong , Alexandre Julliard , Stas Sergeev , Fenghua Yu , "Ravi V. Shankar" , Shuah Khan , linux-kernel@vger.kernel.org, x86@kernel.org, linux-msdos@vger.kernel.org, wine-devel@winehq.org, Tony Luck Subject: Re: [PATCH v7 24/26] x86: Enable User-Mode Instruction Prevention Message-ID: <20170609161031.zreugk443o476mkk@pd.tnic> References: <20170505181724.55000-1-ricardo.neri-calderon@linux.intel.com> <20170505181724.55000-25-ricardo.neri-calderon@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170505181724.55000-25-ricardo.neri-calderon@linux.intel.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 05, 2017 at 11:17:22AM -0700, Ricardo Neri wrote: > User_mode Instruction Prevention (UMIP) is enabled by setting/clearing a > bit in %cr4. > > It makes sense to enable UMIP at some point while booting, before user > spaces come up. Like SMAP and SMEP, is not critical to have it enabled > very early during boot. This is because UMIP is relevant only when there is > a userspace to be protected from. Given the similarities in relevance, it > makes sense to enable UMIP along with SMAP and SMEP. > > UMIP is enabled by default. It can be disabled by adding clearcpuid=514 > to the kernel parameters. > > Cc: Andy Lutomirski > Cc: Andrew Morton > Cc: H. Peter Anvin > Cc: Borislav Petkov > Cc: Brian Gerst > Cc: Chen Yucong > Cc: Chris Metcalf > Cc: Dave Hansen > Cc: Fenghua Yu > Cc: Huang Rui > Cc: Jiri Slaby > Cc: Jonathan Corbet > Cc: Michael S. Tsirkin > Cc: Paul Gortmaker > Cc: Peter Zijlstra > Cc: Ravi V. Shankar > Cc: Shuah Khan > Cc: Vlastimil Babka > Cc: Tony Luck > Cc: Paolo Bonzini > Cc: Liang Z. Li > Cc: Alexandre Julliard > Cc: Stas Sergeev > Cc: x86@kernel.org > Cc: linux-msdos@vger.kernel.org > Signed-off-by: Ricardo Neri > --- > arch/x86/Kconfig | 10 ++++++++++ > arch/x86/kernel/cpu/common.c | 16 +++++++++++++++- > 2 files changed, 25 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 702002b..1b1bbeb 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -1745,6 +1745,16 @@ config X86_SMAP > > If unsure, say Y. > > +config X86_INTEL_UMIP > + def_bool y That's a bit too much. It makes sense on distro kernels but how many machines out there actually have UMIP? > + depends on CPU_SUP_INTEL > + prompt "Intel User Mode Instruction Prevention" if EXPERT > + ---help--- > + The User Mode Instruction Prevention (UMIP) is a security > + feature in newer Intel processors. If enabled, a general > + protection fault is issued if the instructions SGDT, SLDT, > + SIDT, SMSW and STR are executed in user mode. > + > config X86_INTEL_MPX > prompt "Intel MPX (Memory Protection Extensions)" > def_bool n > diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c > index 8ee3211..66ebded 100644 > --- a/arch/x86/kernel/cpu/common.c > +++ b/arch/x86/kernel/cpu/common.c > @@ -311,6 +311,19 @@ static __always_inline void setup_smap(struct cpuinfo_x86 *c) > } > } > > +static __always_inline void setup_umip(struct cpuinfo_x86 *c) > +{ > + if (cpu_feature_enabled(X86_FEATURE_UMIP) && > + cpu_has(c, X86_FEATURE_UMIP)) Hmm, so if UMIP is not build-time disabled, the cpu_feature_enabled() will call static_cpu_has(). Looks like you want to call cpu_has() too because alternatives haven't run yet and static_cpu_has() will reply wrong. Please state that in a comment. -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --