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=-9.8 required=3.0 tests=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 1242BC8300A for ; Wed, 29 Apr 2020 22:09:13 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D01DB214AF for ; Wed, 29 Apr 2020 22:09:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D01DB214AF 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 745AD8E0015; Wed, 29 Apr 2020 18:08:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6CC658E000E; Wed, 29 Apr 2020 18:08:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 548908E0015; Wed, 29 Apr 2020 18:08:50 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0176.hostedemail.com [216.40.44.176]) by kanga.kvack.org (Postfix) with ESMTP id 36DB68E000E for ; Wed, 29 Apr 2020 18:08:50 -0400 (EDT) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id E7216181AC9CB for ; Wed, 29 Apr 2020 22:08:49 +0000 (UTC) X-FDA: 76762283178.20.rail23_12d38dcc90216 X-HE-Tag: rail23_12d38dcc90216 X-Filterd-Recvd-Size: 5714 Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by imf31.hostedemail.com (Postfix) with ESMTP for ; Wed, 29 Apr 2020 22:08:49 +0000 (UTC) IronPort-SDR: rsytLkw+EAsltfP1U9PcXH8iPbJRUTMoVFUvI5HqonTATxjwEPv0nUAfWbad+is+YnQWwgrZ7W vqLsDEVxU6UA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Apr 2020 15:08:48 -0700 IronPort-SDR: wUPVS6TcPPbWAbooMO8NjtL8Z4wUCmoBJDKvJwh8pI0Ugdlvf7Cmbj8k5QRjSmB+Y+2bKrQAYs h3mXof4ZmPLw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,333,1583222400"; d="scan'208";a="276308906" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by orsmga002.jf.intel.com with ESMTP; 29 Apr 2020 15:08:48 -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 Cc: Yu-cheng Yu Subject: [PATCH v10 16/26] mm: Add guard pages around a shadow stack. Date: Wed, 29 Apr 2020 15:07:22 -0700 Message-Id: <20200429220732.31602-17-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20200429220732.31602-1-yu-cheng.yu@intel.com> References: <20200429220732.31602-1-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 --- v10: - Define ARCH_SHADOW_STACK_GUARD_GAP. 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 3bcf27caf6c9..eb9536f803f9 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -907,6 +907,16 @@ 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 f0669e3cdd37..68eadf2c466d 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2630,6 +2630,10 @@ void page_cache_async_readahead(struct address_spa= ce *mapping, pgoff_t offset, unsigned long size); =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); @@ -2662,9 +2666,15 @@ 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; } @@ -2674,9 +2684,15 @@ 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