From patchwork Wed Mar 10 22:00:32 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: 12129561 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 7104FC433DB for ; Wed, 10 Mar 2021 22:01:59 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1C6CE64FAB for ; Wed, 10 Mar 2021 22:01:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1C6CE64FAB 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 296BA8D022A; Wed, 10 Mar 2021 17:01:24 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 20AEE8D022B; Wed, 10 Mar 2021 17:01:24 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D56418D022C; Wed, 10 Mar 2021 17:01:23 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0171.hostedemail.com [216.40.44.171]) by kanga.kvack.org (Postfix) with ESMTP id B50DF8D022A for ; Wed, 10 Mar 2021 17:01:23 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 7EDCB1DFA for ; Wed, 10 Mar 2021 22:01:23 +0000 (UTC) X-FDA: 77905336446.27.0B284AC Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by imf10.hostedemail.com (Postfix) with ESMTP id A43AF4080F5B for ; Wed, 10 Mar 2021 22:01:17 +0000 (UTC) IronPort-SDR: Tc0yuzW7/CU31AHQftCfxUDnPY2RDFLIDaK5huz+o82p6zLv6aDLBjf55TA6JCW3W4Sc3blTZQ qlJhVD8qVdZg== X-IronPort-AV: E=McAfee;i="6000,8403,9919"; a="167846446" X-IronPort-AV: E=Sophos;i="5.81,238,1610438400"; d="scan'208";a="167846446" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Mar 2021 14:01:16 -0800 IronPort-SDR: bQ2V+8czIpOx5l25fkQhzDVwoYoCJCfkkAjGQAWWFu/a7UzElTYoTGT1yGq1R5ZOeWrTa+mn5b YMhD2BOLJF6Q== X-IronPort-AV: E=Sophos;i="5.81,238,1610438400"; d="scan'208";a="403847622" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Mar 2021 14:01:15 -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 , Haitao Huang Cc: Yu-cheng Yu Subject: [PATCH v22 14/28] x86/mm: Shadow Stack page fault error checking Date: Wed, 10 Mar 2021 14:00:32 -0800 Message-Id: <20210310220046.15866-15-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20210310220046.15866-1-yu-cheng.yu@intel.com> References: <20210310220046.15866-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 X-Stat-Signature: cy8pqpymze1m9r3n8x4ehq9ciodu5cuy X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A43AF4080F5B Received-SPF: none (intel.com>: No applicable sender policy available) receiver=imf10; identity=mailfrom; envelope-from=""; helo=mga12.intel.com; client-ip=192.55.52.136 X-HE-DKIM-Result: none/none X-HE-Tag: 1615413677-434585 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: Shadow stack accesses are those that are performed by the CPU where it expects to encounter a shadow stack mapping. These accesses are performed implicitly by CALL/RET at the site of the shadow stack pointer. These accesses are made explicitly by shadow stack management instructions like WRUSSQ. Shadow stacks accesses to shadow-stack mapping can see faults in normal, valid operation just like regular accesses to regular mappings. Shadow stacks need some of the same features like delayed allocation, swap and copy-on-write. Shadow stack accesses can also result in errors, such as when a shadow stack overflows, or if a shadow stack access occurs to a non-shadow-stack mapping. In handling a shadow stack page fault, verify it occurs within a shadow stack mapping. It is always an error otherwise. For valid shadow stack accesses, set FAULT_FLAG_WRITE to effect copy-on-write. Because clearing _PAGE_DIRTY (vs. _PAGE_RW) is used to trigger the fault, shadow stack read fault and shadow stack write fault are not differentiated and both are handled as a write access. Signed-off-by: Yu-cheng Yu Reviewed-by: Kees Cook --- arch/x86/include/asm/trap_pf.h | 2 ++ arch/x86/mm/fault.c | 19 +++++++++++++++++++ 2 files changed, 21 insertions(+) diff --git a/arch/x86/include/asm/trap_pf.h b/arch/x86/include/asm/trap_pf.h index 10b1de500ab1..afa524325e55 100644 --- a/arch/x86/include/asm/trap_pf.h +++ b/arch/x86/include/asm/trap_pf.h @@ -11,6 +11,7 @@ * bit 3 == 1: use of reserved bit detected * bit 4 == 1: fault was an instruction fetch * bit 5 == 1: protection keys block access + * bit 6 == 1: shadow stack access fault * bit 15 == 1: SGX MMU page-fault */ enum x86_pf_error_code { @@ -20,6 +21,7 @@ enum x86_pf_error_code { X86_PF_RSVD = 1 << 3, X86_PF_INSTR = 1 << 4, X86_PF_PK = 1 << 5, + X86_PF_SHSTK = 1 << 6, X86_PF_SGX = 1 << 15, }; diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index a73347e2cdfc..4316732a18c6 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1100,6 +1100,17 @@ access_error(unsigned long error_code, struct vm_area_struct *vma) (error_code & X86_PF_INSTR), foreign)) return 1; + /* + * Verify a shadow stack access is within a shadow stack VMA. + * It is always an error otherwise. Normal data access to a + * shadow stack area is checked in the case followed. + */ + if (error_code & X86_PF_SHSTK) { + if (!(vma->vm_flags & VM_SHSTK)) + return 1; + return 0; + } + if (error_code & X86_PF_WRITE) { /* write, present and write, not present: */ if (unlikely(!(vma->vm_flags & VM_WRITE))) @@ -1293,6 +1304,14 @@ void do_user_addr_fault(struct pt_regs *regs, perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); + /* + * Clearing _PAGE_DIRTY is used to detect shadow stack access. + * This method cannot distinguish shadow stack read vs. write. + * For valid shadow stack accesses, set FAULT_FLAG_WRITE to effect + * copy-on-write. + */ + if (error_code & X86_PF_SHSTK) + flags |= FAULT_FLAG_WRITE; if (error_code & X86_PF_WRITE) flags |= FAULT_FLAG_WRITE; if (error_code & X86_PF_INSTR)