From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751802AbdKFCaN (ORCPT ); Sun, 5 Nov 2017 21:30:13 -0500 Received: from mga09.intel.com ([134.134.136.24]:25011 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751434AbdKFCaL (ORCPT ); Sun, 5 Nov 2017 21:30:11 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.44,350,1505804400"; d="scan'208";a="1033836889" 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, Tony Luck , Ricardo Neri , Fenghua Yu Subject: [PATCH v11 09/12] x86: Enable User-Mode Instruction Prevention at runtime Date: Sun, 5 Nov 2017 18:27:54 -0800 Message-Id: <1509935277-22138-10-git-send-email-ricardo.neri-calderon@linux.intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1509935277-22138-1-git-send-email-ricardo.neri-calderon@linux.intel.com> References: <1509935277-22138-1-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 user space to be protected from. Given these similarities, UMIP can be enabled along with SMAP and SMEP. At the moment, UMIP is disabled by default at build time. 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 38da9bb..f08977d 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1804,6 +1804,16 @@ 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 f8bea7f..13ae9e5 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