From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: [PATCH 3.16 54/76] x86: Introduce barrier_nospec Date: Mon, 12 Mar 2018 03:06:12 +0000 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, Kees Cook , kernel-hardening@lists.openwall.com, Al Viro , Linus Torvalds , Andi Kleen , Ingo Molnar , Dan Williams , alan@linux.intel.com, Thomas Gleixner , Tom Lendacky , linux-arch@vger.kernel.org, gregkh@linuxfoundation.org List-Id: linux-arch.vger.kernel.org 3.16.56-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Dan Williams commit b3d7ad85b80bbc404635dca80f5b129f6242bc7a upstream. Rename the open coded form of this instruction sequence from rdtsc_ordered() into a generic barrier primitive, barrier_nospec(). One of the mitigations for Spectre variant1 vulnerabilities is to fence speculative execution after successfully validating a bounds check. I.e. force the result of a bounds check to resolve in the instruction pipeline to ensure speculative execution honors that result before potentially operating on out-of-bounds data. No functional changes. Suggested-by: Linus Torvalds Suggested-by: Andi Kleen Suggested-by: Ingo Molnar Signed-off-by: Dan Williams Signed-off-by: Thomas Gleixner Cc: linux-arch@vger.kernel.org Cc: Tom Lendacky Cc: Kees Cook Cc: kernel-hardening@lists.openwall.com Cc: gregkh@linuxfoundation.org Cc: Al Viro Cc: alan@linux.intel.com Link: https://lkml.kernel.org/r/151727415361.33451.9049453007262764675.stgit@dwillia2-desk3.amr.corp.intel.com [bwh: Backported to 3.16: update rdtsc_barrier() instead of rdtsc_ordered()] Signed-off-by: Ben Hutchings --- --- a/arch/x86/include/asm/barrier.h +++ b/arch/x86/include/asm/barrier.h @@ -48,6 +48,10 @@ static inline unsigned long array_index_ /* Override the default implementation from linux/nospec.h. */ #define array_index_mask_nospec array_index_mask_nospec +/* Prevent speculative execution past this barrier. */ +#define barrier_nospec() alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC, \ + "lfence", X86_FEATURE_LFENCE_RDTSC) + /** * read_barrier_depends - Flush all pending reads that subsequents reads * depend on. @@ -174,8 +178,7 @@ do { \ */ static __always_inline void rdtsc_barrier(void) { - alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC); - alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC); + barrier_nospec(); } #endif /* _ASM_X86_BARRIER_H */ From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:42770 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932703AbeCLD2S (ORCPT ); Sun, 11 Mar 2018 23:28:18 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings Date: Mon, 12 Mar 2018 03:06:12 +0000 Message-ID: Subject: [PATCH 3.16 54/76] x86: Introduce barrier_nospec In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, Kees Cook , kernel-hardening@lists.openwall.com, Al Viro , Linus Torvalds , Andi Kleen , Ingo Molnar , Dan Williams , alan@linux.intel.com, Thomas Gleixner , Tom Lendacky , linux-arch@vger.kernel.org, gregkh@linuxfoundation.org Message-ID: <20180312030612.rpyB0F2N64Z3dcDdFJi69MJOoewvvwGvH-ccergD69Y@z> 3.16.56-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Dan Williams commit b3d7ad85b80bbc404635dca80f5b129f6242bc7a upstream. Rename the open coded form of this instruction sequence from rdtsc_ordered() into a generic barrier primitive, barrier_nospec(). One of the mitigations for Spectre variant1 vulnerabilities is to fence speculative execution after successfully validating a bounds check. I.e. force the result of a bounds check to resolve in the instruction pipeline to ensure speculative execution honors that result before potentially operating on out-of-bounds data. No functional changes. Suggested-by: Linus Torvalds Suggested-by: Andi Kleen Suggested-by: Ingo Molnar Signed-off-by: Dan Williams Signed-off-by: Thomas Gleixner Cc: linux-arch@vger.kernel.org Cc: Tom Lendacky Cc: Kees Cook Cc: kernel-hardening@lists.openwall.com Cc: gregkh@linuxfoundation.org Cc: Al Viro Cc: alan@linux.intel.com Link: https://lkml.kernel.org/r/151727415361.33451.9049453007262764675.stgit@dwillia2-desk3.amr.corp.intel.com [bwh: Backported to 3.16: update rdtsc_barrier() instead of rdtsc_ordered()] Signed-off-by: Ben Hutchings --- --- a/arch/x86/include/asm/barrier.h +++ b/arch/x86/include/asm/barrier.h @@ -48,6 +48,10 @@ static inline unsigned long array_index_ /* Override the default implementation from linux/nospec.h. */ #define array_index_mask_nospec array_index_mask_nospec +/* Prevent speculative execution past this barrier. */ +#define barrier_nospec() alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC, \ + "lfence", X86_FEATURE_LFENCE_RDTSC) + /** * read_barrier_depends - Flush all pending reads that subsequents reads * depend on. @@ -174,8 +178,7 @@ do { \ */ static __always_inline void rdtsc_barrier(void) { - alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC); - alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC); + barrier_nospec(); } #endif /* _ASM_X86_BARRIER_H */