From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932704AbdJ0XyH (ORCPT ); Fri, 27 Oct 2017 19:54:07 -0400 Received: from mga04.intel.com ([192.55.52.120]:48508 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932577AbdJ0XxH (ORCPT ); Fri, 27 Oct 2017 19:53:07 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.44,306,1505804400"; d="scan'208";a="168215049" From: Ricardo Neri To: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Andy Lutomirski , Borislav Petkov Cc: 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 , "Ravi V. Shankar" , Shuah Khan , linux-kernel@vger.kernel.org, x86@kernel.org, ricardo.neri@intel.com, Ricardo Neri , Fenghua Yu , Tony Luck Subject: [PATCH v10 10/13] x86: Enable User-Mode Instruction Prevention Date: Fri, 27 Oct 2017 16:51:47 -0700 Message-Id: <1509148310-30862-11-git-send-email-ricardo.neri-calderon@linux.intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1509148310-30862-1-git-send-email-ricardo.neri-calderon@linux.intel.com> References: <1509148310-30862-1-git-send-email-ricardo.neri-calderon@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. At the moment, UMIP is disabled by default. It can be enabled at build time by selecting CONFIG_X86_INTEL_UMIP. If enabled at build time, it can be disabled at run time 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: x86@kernel.org Signed-off-by: Ricardo Neri --- arch/x86/Kconfig | 10 ++++++++++ arch/x86/kernel/cpu/common.c | 25 ++++++++++++++++++++++++- 2 files changed, 34 insertions(+), 1 deletion(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index ecf2cf3..1579a71 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1803,6 +1803,16 @@ config X86_SMAP If unsure, say Y. +config X86_INTEL_UMIP + def_bool n + 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 09b8a99..3e6b9ca 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -329,6 +329,28 @@ static __always_inline void setup_smap(struct cpuinfo_x86 *c) } } +static __always_inline void setup_umip(struct cpuinfo_x86 *c) +{ + /* Check the boot processor, plus build option for UMIP. */ + if (!cpu_feature_enabled(X86_FEATURE_UMIP)) + goto out; + + /* Check the current processor's cpuid bits. */ + if (!cpu_has(c, X86_FEATURE_UMIP)) + goto out; + + cr4_set_bits(X86_CR4_UMIP); + + return; + +out: + /* + * Make sure UMIP is disabled in case it was enabled in a + * previous boot (e.g., via kexec). + */ + cr4_clear_bits(X86_CR4_UMIP); +} + /* * Protection Keys are not available in 32-bit mode. */ @@ -1147,9 +1169,10 @@ static void identify_cpu(struct cpuinfo_x86 *c) /* Disable the PN if appropriate */ squash_the_stupid_serial_number(c); - /* Set up SMEP/SMAP */ + /* Set up SMEP/SMAP/UMIP */ setup_smep(c); setup_smap(c); + setup_umip(c); /* * The vendor-specific functions might have changed features. -- 2.7.4