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=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 CFC2DC4338F for ; Fri, 20 Aug 2021 18:19:25 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 86DFC61209 for ; Fri, 20 Aug 2021 18:19:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 86DFC61209 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 61F528D000E; Fri, 20 Aug 2021 14:18:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5FC598D000D; Fri, 20 Aug 2021 14:18:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3DE7D8D000E; Fri, 20 Aug 2021 14:18:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0081.hostedemail.com [216.40.44.81]) by kanga.kvack.org (Postfix) with ESMTP id 096DE8D000D for ; Fri, 20 Aug 2021 14:18:53 -0400 (EDT) Received: from smtpin36.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id B735780B9A03 for ; Fri, 20 Aug 2021 18:18:52 +0000 (UTC) X-FDA: 78496270104.36.5E148C3 Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by imf17.hostedemail.com (Postfix) with ESMTP id 25DBFF00038C for ; Fri, 20 Aug 2021 18:18:52 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10082"; a="196398711" X-IronPort-AV: E=Sophos;i="5.84,338,1620716400"; d="scan'208";a="196398711" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Aug 2021 11:18:50 -0700 X-IronPort-AV: E=Sophos;i="5.84,338,1620716400"; d="scan'208";a="533074738" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Aug 2021 11:18:49 -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" , Dave Martin , Weijiang Yang , Pengfei Xu , Haitao Huang , Rick P Edgecombe Cc: Yu-cheng Yu , "Kirill A . Shutemov" Subject: [PATCH v29 18/32] mm: Add guard pages around a shadow stack. Date: Fri, 20 Aug 2021 11:11:47 -0700 Message-Id: <20210820181201.31490-19-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20210820181201.31490-1-yu-cheng.yu@intel.com> References: <20210820181201.31490-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 Authentication-Results: imf17.hostedemail.com; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=intel.com (policy=none); spf=none (imf17.hostedemail.com: domain of yu-cheng.yu@intel.com has no SPF policy when checking 192.55.52.136) smtp.mailfrom=yu-cheng.yu@intel.com X-Stat-Signature: i9ezqzq1is4akr66to89ch7ajz7pw6z9 X-Rspamd-Queue-Id: 25DBFF00038C X-Rspamd-Server: rspam05 X-HE-Tag: 1629483532-599207 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 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/pag= e_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, unsi= gned long end_pfn); =20 extern void initmem_init(void); =20 +#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__ */ =20 #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 =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 SHADOW_STACK_GUARD_GAP PAGE_SIZE + +unsigned long vm_start_gap(struct vm_area_struct *vma) +{ + unsigned long vm_start =3D vma->vm_start; + unsigned long gap =3D 0; + + if (vma->vm_flags & VM_GROWSDOWN) + gap =3D stack_guard_gap; + else if (vma->vm_flags & VM_SHADOW_STACK) + gap =3D SHADOW_STACK_GUARD_GAP; + + if (gap !=3D 0) { + vm_start -=3D gap; + if (vm_start > vma->vm_start) + vm_start =3D 0; + } + return vm_start; +} + +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_SHADOW_STACK) + gap =3D SHADOW_STACK_GUARD_GAP; + + if (gap !=3D 0) { + vm_end +=3D gap; + if (vm_end < vma->vm_end) + vm_end =3D -PAGE_SIZE; + } + return vm_end; +} diff --git a/include/linux/mm.h b/include/linux/mm.h index 4548f75cef14..354f38d21eed 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2729,6 +2729,7 @@ struct vm_area_struct *vma_lookup(struct mm_struct = *mm, unsigned long addr) return vma; } =20 +#ifndef vm_start_gap static inline unsigned long vm_start_gap(struct vm_area_struct *vma) { unsigned long vm_start =3D vma->vm_start; @@ -2740,7 +2741,9 @@ static inline unsigned long vm_start_gap(struct vm_= area_struct *vma) } return vm_start; } +#endif =20 +#ifndef vm_end_gap static inline unsigned long vm_end_gap(struct vm_area_struct *vma) { unsigned long vm_end =3D vma->vm_end; @@ -2752,6 +2755,7 @@ static inline unsigned long vm_end_gap(struct vm_ar= ea_struct *vma) } return vm_end; } +#endif =20 static inline unsigned long vma_pages(struct vm_area_struct *vma) { --=20 2.21.0