From patchwork Tue Apr 27 20:43:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu-cheng Yu X-Patchwork-Id: 12227257 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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 A2D46C433ED for ; Tue, 27 Apr 2021 20:44:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4E450613FE for ; Tue, 27 Apr 2021 20:44:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4E450613FE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A14DE6B0085; Tue, 27 Apr 2021 16:44:20 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9A2736B0087; Tue, 27 Apr 2021 16:44:20 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6DFDB6B0088; Tue, 27 Apr 2021 16:44:20 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0236.hostedemail.com [216.40.44.236]) by kanga.kvack.org (Postfix) with ESMTP id 497ED6B0085 for ; Tue, 27 Apr 2021 16:44:20 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 05D0B181AEF00 for ; Tue, 27 Apr 2021 20:44:20 +0000 (UTC) X-FDA: 78079324680.22.6B83B82 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by imf21.hostedemail.com (Postfix) with ESMTP id 15772E00012B for ; Tue, 27 Apr 2021 20:44:15 +0000 (UTC) IronPort-SDR: UuIn8mAry5C89OMP7Tehg4tCC0PfH0yFZ1rdt/IC8ITH8RCCohInH7tE/Lw25vZ4Kux6W6ZpYh sBi7kVLEtEeA== X-IronPort-AV: E=McAfee;i="6200,9189,9967"; a="194473691" X-IronPort-AV: E=Sophos;i="5.82,255,1613462400"; d="scan'208";a="194473691" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Apr 2021 13:44:18 -0700 IronPort-SDR: X4XEh26uRW5SCsYJRhadYcziflBR+F11pNRCZDRYRlgwXTEVWFoSxTpPvuUGbuSOsrdopsYXxB YvOdSAUtODww== X-IronPort-AV: E=Sophos;i="5.82,255,1613462400"; d="scan'208";a="465623524" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Apr 2021 13:44:16 -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 v26 17/30] mm: Add guard pages around a shadow stack. Date: Tue, 27 Apr 2021 13:43:02 -0700 Message-Id: <20210427204315.24153-18-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20210427204315.24153-1-yu-cheng.yu@intel.com> References: <20210427204315.24153-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 X-Stat-Signature: ia6ktm6o4sdg98g6ez9us4jfioheind1 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 15772E00012B Received-SPF: none (intel.com>: No applicable sender policy available) receiver=imf21; identity=mailfrom; envelope-from=""; helo=mga04.intel.com; client-ip=192.55.52.120 X-HE-DKIM-Result: none/none X-HE-Tag: 1619556255-871200 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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, 57 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..81f9325084d3 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) {