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=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 4AB8CC352B9 for ; Mon, 12 Oct 2020 15:40:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 01E5620575 for ; Mon, 12 Oct 2020 15:40:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 01E5620575 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 BFB37940011; Mon, 12 Oct 2020 11:39:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AB9C894000F; Mon, 12 Oct 2020 11:39:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9A9CC940011; Mon, 12 Oct 2020 11:39:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0168.hostedemail.com [216.40.44.168]) by kanga.kvack.org (Postfix) with ESMTP id 5F49694000F for ; Mon, 12 Oct 2020 11:39:57 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id CCAFF3623 for ; Mon, 12 Oct 2020 15:39:56 +0000 (UTC) X-FDA: 77363683992.13.smash80_17123be271fb Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin13.hostedemail.com (Postfix) with ESMTP id A9E6718140B67 for ; Mon, 12 Oct 2020 15:39:56 +0000 (UTC) X-HE-Tag: smash80_17123be271fb X-Filterd-Recvd-Size: 5919 Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by imf50.hostedemail.com (Postfix) with ESMTP for ; Mon, 12 Oct 2020 15:39:56 +0000 (UTC) IronPort-SDR: CQWMs0fSg9fXAeK33Q8P7JBsxr5BR7RLo2VgLCpXBCeeZoahV0hzWCnZIdOD/wTJadVoeBn1BM vfkU9XAc98aQ== X-IronPort-AV: E=McAfee;i="6000,8403,9772"; a="152686151" X-IronPort-AV: E=Sophos;i="5.77,367,1596524400"; d="scan'208";a="152686151" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Oct 2020 08:39:54 -0700 IronPort-SDR: uWaSeHh1uSCgF6U+F52fJpCp8vsAHiDtGJSNbdZ0NxIo+NYLri10Ld2Uzl+KfWsg0yDrmE22I6 08cRUO3IJegQ== X-IronPort-AV: E=Sophos;i="5.77,367,1596524400"; d="scan'208";a="530010883" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Oct 2020 08:39:54 -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 Cc: Yu-cheng Yu Subject: [PATCH v14 16/26] mm: Add guard pages around a shadow stack. Date: Mon, 12 Oct 2020 08:38:40 -0700 Message-Id: <20201012153850.26996-17-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20201012153850.26996-1-yu-cheng.yu@intel.com> References: <20201012153850.26996-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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 memor= y areas. The maximum moving distance by INCSSPQ is 255 * 8 =3D 2040 bytes and 255 * 4 =3D 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 --- arch/x86/include/asm/processor.h | 10 ++++++++++ include/linux/mm.h | 24 ++++++++++++++++++++---- 2 files changed, 30 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/proc= essor.h index 97143d87994c..01acbd63cad8 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -840,6 +840,16 @@ static inline void spin_lock_prefetch(const void *x) #define STACK_TOP TASK_SIZE_LOW #define STACK_TOP_MAX TASK_SIZE_MAX =20 +/* + * Shadow stack pointer is moved by CALL, JMP, and INCSSP(Q/D). INCSSPQ + * moves shadow stack pointer up to 255 * 8 =3D ~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 ARCH_SHADOW_STACK_GUARD_GAP PAGE_SIZE + #define INIT_THREAD { \ .addr_limit =3D KERNEL_DS, \ } diff --git a/include/linux/mm.h b/include/linux/mm.h index 4f6305106feb..ce461795fd8b 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2615,6 +2615,10 @@ extern vm_fault_t filemap_page_mkwrite(struct vm_f= ault *vmf); int __must_check write_one_page(struct page *page); void task_dirty_inc(struct task_struct *tsk); =20 +#ifndef ARCH_SHADOW_STACK_GUARD_GAP +#define ARCH_SHADOW_STACK_GUARD_GAP 0 +#endif + extern unsigned long stack_guard_gap; /* Generic expand stack which grows the stack according to GROWS{UP,DOWN= } */ extern int expand_stack(struct vm_area_struct *vma, unsigned long addres= s); @@ -2647,9 +2651,15 @@ static inline struct vm_area_struct * find_vma_int= ersection(struct mm_struct * m static inline unsigned long vm_start_gap(struct vm_area_struct *vma) { unsigned long vm_start =3D vma->vm_start; + unsigned long gap =3D 0; =20 - if (vma->vm_flags & VM_GROWSDOWN) { - vm_start -=3D stack_guard_gap; + if (vma->vm_flags & VM_GROWSDOWN) + gap =3D stack_guard_gap; + else if (vma->vm_flags & VM_SHSTK) + gap =3D ARCH_SHADOW_STACK_GUARD_GAP; + + if (gap !=3D 0) { + vm_start -=3D gap; if (vm_start > vma->vm_start) vm_start =3D 0; } @@ -2659,9 +2669,15 @@ static inline unsigned long vm_start_gap(struct vm= _area_struct *vma) static inline unsigned long vm_end_gap(struct vm_area_struct *vma) { unsigned long vm_end =3D vma->vm_end; + unsigned long gap =3D 0; + + if (vma->vm_flags & VM_GROWSUP) + gap =3D stack_guard_gap; + else if (vma->vm_flags & VM_SHSTK) + gap =3D ARCH_SHADOW_STACK_GUARD_GAP; =20 - if (vma->vm_flags & VM_GROWSUP) { - vm_end +=3D stack_guard_gap; + if (gap !=3D 0) { + vm_end +=3D gap; if (vm_end < vma->vm_end) vm_end =3D -PAGE_SIZE; } --=20 2.21.0