From patchwork Mon Aug 30 18:15:28 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: 12465771 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 3BA0FC43214 for ; Mon, 30 Aug 2021 18:17:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D482360FD9 for ; Mon, 30 Aug 2021 18:17:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org D482360FD9 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 2D1346B009F; Mon, 30 Aug 2021 14:16:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2A8086B00A0; Mon, 30 Aug 2021 14:16:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 147008D0001; Mon, 30 Aug 2021 14:16:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0093.hostedemail.com [216.40.44.93]) by kanga.kvack.org (Postfix) with ESMTP id F36096B00A0 for ; Mon, 30 Aug 2021 14:16:27 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id B6F991802EFDE for ; Mon, 30 Aug 2021 18:16:27 +0000 (UTC) X-FDA: 78532552014.24.2266BED Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by imf13.hostedemail.com (Postfix) with ESMTP id 1070B1021633 for ; Mon, 30 Aug 2021 18:16:26 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10092"; a="205545913" X-IronPort-AV: E=Sophos;i="5.84,364,1620716400"; d="scan'208";a="205545913" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Aug 2021 11:16:23 -0700 X-IronPort-AV: E=Sophos;i="5.84,364,1620716400"; d="scan'208";a="530533383" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Aug 2021 11:16:23 -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 v30 32/32] mm: Introduce PROT_SHADOW_STACK for shadow stack Date: Mon, 30 Aug 2021 11:15:28 -0700 Message-Id: <20210830181528.1569-33-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20210830181528.1569-1-yu-cheng.yu@intel.com> References: <20210830181528.1569-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 Authentication-Results: imf13.hostedemail.com; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=intel.com (policy=none); spf=none (imf13.hostedemail.com: domain of yu-cheng.yu@intel.com has no SPF policy when checking 134.134.136.20) smtp.mailfrom=yu-cheng.yu@intel.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 1070B1021633 X-Stat-Signature: ca97m3cnihuwko9hzofzjstt41ziupxo X-HE-Tag: 1630347386-796970 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_SHADOW_STACK to mmap() and 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_SHADOW_STACK to mmap()/mprotect() takes advantage of existing APIs. The x86-specific PROT_SHADOW_STACK is translated to VM_SHADOW_STACK 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. [1] https://lore.kernel.org/lkml/20200828121624.108243-1-hjl.tools@gmail.com/ Signed-off-by: Yu-cheng Yu Reviewed-by: Kirill A. Shutemov Cc: Kees Cook --- arch/x86/include/asm/mman.h | 60 +++++++++++++++++++++++++++++++- arch/x86/include/uapi/asm/mman.h | 2 ++ include/linux/mm.h | 1 + 3 files changed, 62 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/mman.h b/arch/x86/include/asm/mman.h index 629f6c81263a..b77933923b9a 100644 --- a/arch/x86/include/asm/mman.h +++ b/arch/x86/include/asm/mman.h @@ -20,11 +20,69 @@ ((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) ( \ +#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_SHADOW_STACK) + vm_prot_bits |= VM_SHADOW_STACK; + + return vm_prot_bits; +} + +#define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey) + +#ifdef CONFIG_X86_SHADOW_STACK +static inline bool arch_validate_prot(unsigned long prot, unsigned long addr) +{ + unsigned long valid = PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM | + PROT_SHADOW_STACK; + + if (prot & ~valid) + return false; + + if (prot & PROT_SHADOW_STACK) { + if (!current->thread.shstk.size) + return false; + + /* + * A shadow stack mapping is indirectly writable by only + * the CALL and WRUSS instructions, but not other write + * instructions). PROT_SHADOW_STACK and PROT_WRITE are + * mutually exclusive. + */ + if (prot & PROT_WRITE) + return false; + } + + return true; +} + +#define arch_validate_prot arch_validate_prot + +static inline bool arch_validate_flags(struct vm_area_struct *vma, unsigned long vm_flags) +{ + /* + * Shadow stack must be anonymous and not shared. + */ + if ((vm_flags & VM_SHADOW_STACK) && !vma_is_anonymous(vma)) + return false; + + return true; +} + +#define arch_validate_flags(vma, vm_flags) arch_validate_flags(vma, vm_flags) + +#endif /* CONFIG_X86_SHADOW_STACK */ + #endif /* _ASM_X86_MMAN_H */ diff --git a/arch/x86/include/uapi/asm/mman.h b/arch/x86/include/uapi/asm/mman.h index f28fa4acaeaf..4c36b263cf0a 100644 --- a/arch/x86/include/uapi/asm/mman.h +++ b/arch/x86/include/uapi/asm/mman.h @@ -4,6 +4,8 @@ #define MAP_32BIT 0x40 /* only give out 32bit addresses */ +#define PROT_SHADOW_STACK 0x10 /* shadow stack pages */ + #include #endif /* _UAPI_ASM_X86_MMAN_H */ diff --git a/include/linux/mm.h b/include/linux/mm.h index 07e642af59d3..041e7e8ff702 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -349,6 +349,7 @@ 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_SHADOW_STACK #elif defined(CONFIG_PPC) # define VM_SAO VM_ARCH_1 /* Strong Access Ordering (powerpc) */ #elif defined(CONFIG_PARISC)