From patchwork Tue Dec 29 21:30:53 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu-cheng Yu X-Patchwork-Id: 11992717 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 E9EA5C433DB for ; Tue, 29 Dec 2020 21:33:21 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9291F20867 for ; Tue, 29 Dec 2020 21:33:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9291F20867 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 E31798D0062; Tue, 29 Dec 2020 16:32:34 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id DE4688D005F; Tue, 29 Dec 2020 16:32:34 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C7F1E8D0062; Tue, 29 Dec 2020 16:32:34 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0022.hostedemail.com [216.40.44.22]) by kanga.kvack.org (Postfix) with ESMTP id AC3208D005F for ; Tue, 29 Dec 2020 16:32:34 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 8179C181AEF0B for ; Tue, 29 Dec 2020 21:32:34 +0000 (UTC) X-FDA: 77647619028.27.bells76_61150032749f Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin27.hostedemail.com (Postfix) with ESMTP id 62B813D663 for ; Tue, 29 Dec 2020 21:32:34 +0000 (UTC) X-HE-Tag: bells76_61150032749f X-Filterd-Recvd-Size: 9492 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by imf29.hostedemail.com (Postfix) with ESMTP for ; Tue, 29 Dec 2020 21:32:33 +0000 (UTC) IronPort-SDR: Wj9RcCK8DAKF6+YmAU9idregqU9n4qCtoR1jm+PBakM+z8irHq7v30Ue+W/AImRM5wWrGHxkTh q+IaOYDcIIdA== X-IronPort-AV: E=McAfee;i="6000,8403,9849"; a="261294182" X-IronPort-AV: E=Sophos;i="5.78,459,1599548400"; d="scan'208";a="261294182" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Dec 2020 13:32:32 -0800 IronPort-SDR: Z2oXFBhoGdxOv9yvq3joG54XWuTMFac7fWUNRS/pr+oFJCM2l4FFx4MqeAGZbFKCkWpX5gXNCU Edx0FA1lKTFQ== X-IronPort-AV: E=Sophos;i="5.78,459,1599548400"; d="scan'208";a="376189679" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Dec 2020 13:32:31 -0800 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 v17 26/26] mm: Introduce PROT_SHSTK for shadow stack Date: Tue, 29 Dec 2020 13:30:53 -0800 Message-Id: <20201229213053.16395-27-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20201229213053.16395-1-yu-cheng.yu@intel.com> References: <20201229213053.16395-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 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: There are three possible options to create a shadow stack allocation API: an arch_prctl, a new syscall, or adding PROT_SHSTK to mmap()/mprotect(). Each has its advantages and compromises. An arch_prctl() is the least intrusive. However, the existing x86 arch_prctl() takes only two parameters. Multiple parameters must be passed in a memory buffer. There is a proposal to pass more parameters in registers [1], but no active discussion on that. A new syscall minimizes compatibility issues and offers an extensible frame work to other architectures, but this will likely result in some overlap of mmap()/mprotect(). The introduction of PROT_SHSTK to mmap()/mprotect() takes advantage of existing APIs. The x86-specific PROT_SHSTK is translated to VM_SHSTK and a shadow stack mapping is created without reinventing the wheel. There are potential pitfalls though. The most obvious one would be using this as a bypass to shadow stack protection. However, the attacker would have to get to the syscall first. Since arch_calc_vm_prot_bits() is modified, I have moved arch_vm_get_page _prot() and arch_calc_vm_prot_bits() to x86/include/asm/mman.h. This will be more consistent with other architectures. [1] https://lore.kernel.org/lkml/20200828121624.108243-1-hjl.tools@gmail.com/ Signed-off-by: Yu-cheng Yu --- arch/x86/include/asm/mman.h | 83 ++++++++++++++++++++++++++++++++ arch/x86/include/uapi/asm/mman.h | 28 ++--------- include/linux/mm.h | 1 + mm/mmap.c | 8 ++- 4 files changed, 95 insertions(+), 25 deletions(-) create mode 100644 arch/x86/include/asm/mman.h diff --git a/arch/x86/include/asm/mman.h b/arch/x86/include/asm/mman.h new file mode 100644 index 000000000000..6cb7801edb4b --- /dev/null +++ b/arch/x86/include/asm/mman.h @@ -0,0 +1,83 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_MMAN_H +#define _ASM_X86_MMAN_H + +#include +#include + +#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS +/* + * Take the 4 protection key bits out of the vma->vm_flags + * value and turn them in to the bits that we can put in + * to a pte. + * + * Only override these if Protection Keys are available + * (which is only on 64-bit). + */ +#define arch_vm_get_page_prot(vm_flags) __pgprot( \ + ((vm_flags) & VM_PKEY_BIT0 ? _PAGE_PKEY_BIT0 : 0) | \ + ((vm_flags) & VM_PKEY_BIT1 ? _PAGE_PKEY_BIT1 : 0) | \ + ((vm_flags) & VM_PKEY_BIT2 ? _PAGE_PKEY_BIT2 : 0) | \ + ((vm_flags) & VM_PKEY_BIT3 ? _PAGE_PKEY_BIT3 : 0)) + +#define pkey_vm_prot_bits(prot, key) ( \ + ((key) & 0x1 ? VM_PKEY_BIT0 : 0) | \ + ((key) & 0x2 ? VM_PKEY_BIT1 : 0) | \ + ((key) & 0x4 ? VM_PKEY_BIT2 : 0) | \ + ((key) & 0x8 ? VM_PKEY_BIT3 : 0)) +#else +#define pkey_vm_prot_bits(prot, key) (0) +#endif + +static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot, + unsigned long pkey) +{ + unsigned long vm_prot_bits = pkey_vm_prot_bits(prot, pkey); + + if (!(prot & PROT_WRITE) && (prot & PROT_SHSTK)) + vm_prot_bits |= VM_SHSTK; + + return vm_prot_bits; +} +#define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey) + +#ifdef CONFIG_X86_CET_USER +static inline bool arch_validate_prot(unsigned long prot, unsigned long addr) +{ + unsigned long valid = PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM; + + if (prot & ~(valid | PROT_SHSTK)) + return false; + + if (prot & PROT_SHSTK) { + struct vm_area_struct *vma; + + if (!current->thread.cet.shstk_size) + return false; + + /* + * A shadow stack mapping is indirectly writable by only + * the CALL and WRUSS instructions, but not other write + * instructions). PROT_SHSTK and PROT_WRITE are mutually + * exclusive. + */ + if (prot & PROT_WRITE) + return false; + + vma = find_vma(current->mm, addr); + if (!vma) + return false; + + /* + * Shadow stack cannot be backed by a file or shared. + */ + if (vma->vm_file || (vma->vm_flags & VM_SHARED)) + return false; + } + + return true; +} +#define arch_validate_prot arch_validate_prot +#endif + +#endif /* _ASM_X86_MMAN_H */ diff --git a/arch/x86/include/uapi/asm/mman.h b/arch/x86/include/uapi/asm/mman.h index d4a8d0424bfb..39bb7db344a6 100644 --- a/arch/x86/include/uapi/asm/mman.h +++ b/arch/x86/include/uapi/asm/mman.h @@ -1,31 +1,11 @@ /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ -#ifndef _ASM_X86_MMAN_H -#define _ASM_X86_MMAN_H +#ifndef _UAPI_ASM_X86_MMAN_H +#define _UAPI_ASM_X86_MMAN_H #define MAP_32BIT 0x40 /* only give out 32bit addresses */ -#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS -/* - * Take the 4 protection key bits out of the vma->vm_flags - * value and turn them in to the bits that we can put in - * to a pte. - * - * Only override these if Protection Keys are available - * (which is only on 64-bit). - */ -#define arch_vm_get_page_prot(vm_flags) __pgprot( \ - ((vm_flags) & VM_PKEY_BIT0 ? _PAGE_PKEY_BIT0 : 0) | \ - ((vm_flags) & VM_PKEY_BIT1 ? _PAGE_PKEY_BIT1 : 0) | \ - ((vm_flags) & VM_PKEY_BIT2 ? _PAGE_PKEY_BIT2 : 0) | \ - ((vm_flags) & VM_PKEY_BIT3 ? _PAGE_PKEY_BIT3 : 0)) - -#define arch_calc_vm_prot_bits(prot, key) ( \ - ((key) & 0x1 ? VM_PKEY_BIT0 : 0) | \ - ((key) & 0x2 ? VM_PKEY_BIT1 : 0) | \ - ((key) & 0x4 ? VM_PKEY_BIT2 : 0) | \ - ((key) & 0x8 ? VM_PKEY_BIT3 : 0)) -#endif +#define PROT_SHSTK 0x10 /* shadow stack pages */ #include -#endif /* _ASM_X86_MMAN_H */ +#endif /* _UAPI_ASM_X86_MMAN_H */ diff --git a/include/linux/mm.h b/include/linux/mm.h index 85d5695c7e2f..34249500c93b 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -335,6 +335,7 @@ extern unsigned int kobjsize(const void *objp); #if defined(CONFIG_X86) # define VM_PAT VM_ARCH_1 /* PAT reserves whole VMA at once (x86) */ +# define VM_ARCH_CLEAR VM_SHSTK #elif defined(CONFIG_PPC) # define VM_SAO VM_ARCH_1 /* Strong Access Ordering (powerpc) */ #elif defined(CONFIG_PARISC) diff --git a/mm/mmap.c b/mm/mmap.c index 95ce7cd68654..9434469db2ce 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1483,6 +1483,12 @@ unsigned long do_mmap(struct file *file, unsigned long addr, struct inode *inode = file_inode(file); unsigned long flags_mask; + /* + * Call stack cannot be backed by a file. + */ + if (vm_flags & VM_SHSTK) + return -EINVAL; + if (!file_mmap_ok(file, inode, pgoff, len)) return -EOVERFLOW; @@ -1547,7 +1553,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr, } else { switch (flags & MAP_TYPE) { case MAP_SHARED: - if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP)) + if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP|VM_SHSTK)) return -EINVAL; /* * Ignore pgoff.