From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 75CC7C43603 for ; Thu, 15 Apr 2021 22:16:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6001D610F7 for ; Thu, 15 Apr 2021 22:16:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236893AbhDOWRR (ORCPT ); Thu, 15 Apr 2021 18:17:17 -0400 Received: from mga14.intel.com ([192.55.52.115]:22370 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234985AbhDOWQv (ORCPT ); Thu, 15 Apr 2021 18:16:51 -0400 IronPort-SDR: Fmbm4sy8a9fK63YYFAgvVapS8S9i6m5fH6AhBE2J8Dc5NNIqTTdmfK1ckrdzOjgFFy0do6Vo0K 0pyjubQfwwDA== X-IronPort-AV: E=McAfee;i="6200,9189,9955"; a="194513366" X-IronPort-AV: E=Sophos;i="5.82,225,1613462400"; d="scan'208";a="194513366" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Apr 2021 15:15:37 -0700 IronPort-SDR: 9WiBEZshtAMDN97srUYWkz8eGsazEbPanaMdCF6rBu9hN8TTPWo41CiLgK86P1kZhwEQW1JFli b4xTMGhaJevA== X-IronPort-AV: E=Sophos;i="5.82,225,1613462400"; d="scan'208";a="451270915" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Apr 2021 15:15:37 -0700 From: Yu-cheng Yu To: 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 , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu , Haitao Huang Cc: Yu-cheng Yu , "Kirill A . Shutemov" Subject: [PATCH v25 17/30] mm: Add guard pages around a shadow stack. Date: Thu, 15 Apr 2021 15:14:06 -0700 Message-Id: <20210415221419.31835-18-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20210415221419.31835-1-yu-cheng.yu@intel.com> References: <20210415221419.31835-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org INCSSP(Q/D) increments shadow stack pointer and 'pops and discards' the first and the last elements in the range, effectively touches those memory areas. The maximum moving distance by INCSSPQ is 255 * 8 = 2040 bytes and 255 * 4 = 1020 bytes by INCSSPD. Both ranges are far from PAGE_SIZE. Thus, putting a gap page on both ends of a shadow stack prevents INCSSP, CALL, and RET from going beyond. Signed-off-by: Yu-cheng Yu Reviewed-by: Kirill A. Shutemov Cc: Kees Cook --- v25: - Move SHADOW_STACK_GUARD_GAP to arch/x86/mm/mmap.c. v24: - Instead changing vm_*_gap(), create x86-specific versions. arch/x86/include/asm/page_types.h | 7 +++++ arch/x86/mm/mmap.c | 46 +++++++++++++++++++++++++++++++ include/linux/mm.h | 4 +++ 3 files changed, 56 insertions(+) diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h index a506a411474d..e1533fdc08b4 100644 --- a/arch/x86/include/asm/page_types.h +++ b/arch/x86/include/asm/page_types.h @@ -73,6 +73,13 @@ bool pfn_range_is_mapped(unsigned long start_pfn, unsigned long end_pfn); extern void initmem_init(void); +#define vm_start_gap vm_start_gap +struct vm_area_struct; +extern unsigned long vm_start_gap(struct vm_area_struct *vma); + +#define vm_end_gap vm_end_gap +extern unsigned long vm_end_gap(struct vm_area_struct *vma); + #endif /* !__ASSEMBLY__ */ #endif /* _ASM_X86_PAGE_DEFS_H */ diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index f3f52c5e2fd6..3f6455d14d18 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -250,3 +250,49 @@ bool pfn_modify_allowed(unsigned long pfn, pgprot_t prot) return false; return true; } + +/* + * Shadow stack pointer is moved by CALL, RET, and INCSSP(Q/D). INCSSPQ + * moves shadow stack pointer up to 255 * 8 = ~2 KB (~1KB for INCSSPD) and + * touches the first and the last element in the range, which triggers a + * page fault if the range is not in a shadow stack. Because of this, + * creating 4-KB guard pages around a shadow stack prevents these + * instructions from going beyond. + */ +#define SHADOW_STACK_GUARD_GAP PAGE_SIZE + +unsigned long vm_start_gap(struct vm_area_struct *vma) +{ + unsigned long vm_start = vma->vm_start; + unsigned long gap = 0; + + if (vma->vm_flags & VM_GROWSDOWN) + gap = stack_guard_gap; + else if (vma->vm_flags & VM_SHADOW_STACK) + gap = SHADOW_STACK_GUARD_GAP; + + if (gap != 0) { + vm_start -= gap; + if (vm_start > vma->vm_start) + vm_start = 0; + } + return vm_start; +} + +unsigned long vm_end_gap(struct vm_area_struct *vma) +{ + unsigned long vm_end = vma->vm_end; + unsigned long gap = 0; + + if (vma->vm_flags & VM_GROWSUP) + gap = stack_guard_gap; + else if (vma->vm_flags & VM_SHADOW_STACK) + gap = SHADOW_STACK_GUARD_GAP; + + if (gap != 0) { + vm_end += gap; + if (vm_end < vma->vm_end) + vm_end = -PAGE_SIZE; + } + return vm_end; +} diff --git a/include/linux/mm.h b/include/linux/mm.h index 6ac9b3e9a865..3e9c84f21ef6 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2660,6 +2660,7 @@ static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * m return vma; } +#ifndef vm_start_gap static inline unsigned long vm_start_gap(struct vm_area_struct *vma) { unsigned long vm_start = vma->vm_start; @@ -2671,7 +2672,9 @@ static inline unsigned long vm_start_gap(struct vm_area_struct *vma) } return vm_start; } +#endif +#ifndef vm_end_gap static inline unsigned long vm_end_gap(struct vm_area_struct *vma) { unsigned long vm_end = vma->vm_end; @@ -2683,6 +2686,7 @@ static inline unsigned long vm_end_gap(struct vm_area_struct *vma) } return vm_end; } +#endif static inline unsigned long vma_pages(struct vm_area_struct *vma) { -- 2.21.0