From patchwork Tue Aug 25 00:25:28 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: 11734533 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D0853913 for ; Tue, 25 Aug 2020 00:30:00 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9D20A207D8 for ; Tue, 25 Aug 2020 00:30:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9D20A207D8 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 A9B18900005; Mon, 24 Aug 2020 20:29:39 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 9AD818E001A; Mon, 24 Aug 2020 20:29:39 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7FE8E8E001B; Mon, 24 Aug 2020 20:29:39 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0062.hostedemail.com [216.40.44.62]) by kanga.kvack.org (Postfix) with ESMTP id 583F08E001A for ; Mon, 24 Aug 2020 20:29:39 -0400 (EDT) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 2297F181AEF1D for ; Tue, 25 Aug 2020 00:29:39 +0000 (UTC) X-FDA: 77187207678.16.stamp24_1b1389d27057 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin16.hostedemail.com (Postfix) with ESMTP id EC46D100E690B for ; Tue, 25 Aug 2020 00:29:38 +0000 (UTC) X-Spam-Summary: 1,0,0,,d41d8cd98f00b204,yu-cheng.yu@intel.com,,RULES_HIT:30003:30054:30056:30064:30069:30070,0,RBL:134.134.136.24:@intel.com:.lbl8.mailshell.net-62.18.0.100 64.95.201.95;04yrchwanhjggw3aq96yfepcwmgwkopd9bf64hsw76mmgnwjyiwo8y8j7cbu4sd.gxpm91jod81ppowoyqkbuyt3puxfeda4qny6xryb8tr91p1y5t5gwzr7p6idfzn.q-lbl8.mailshell.net-223.238.255.100,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:ft,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:23,LUA_SUMMARY:none X-HE-Tag: stamp24_1b1389d27057 X-Filterd-Recvd-Size: 6011 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by imf20.hostedemail.com (Postfix) with ESMTP for ; Tue, 25 Aug 2020 00:29:38 +0000 (UTC) IronPort-SDR: din5q8mfepaaAtDB+WGUg+kb3iP2xWEFqLIcz2yPyIY5hBRFj8pqxfEMo45Zh9xkx0ku84b6lY tqWPMLOT9PcQ== X-IronPort-AV: E=McAfee;i="6000,8403,9723"; a="157061733" X-IronPort-AV: E=Sophos;i="5.76,350,1592895600"; d="scan'208";a="157061733" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Aug 2020 17:29:38 -0700 IronPort-SDR: gyDL0bD4h4WCbMcpj25tslUEs127x3suqMjrmQ0E2yteo22B/UsPr9y0EVQVTIfUjN0EIkSfP0 6V6TH39xotQw== X-IronPort-AV: E=Sophos;i="5.76,350,1592895600"; d="scan'208";a="474134987" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Aug 2020 17:29:37 -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 v11 13/25] x86/mm: Shadow Stack page fault error checking Date: Mon, 24 Aug 2020 17:25:28 -0700 Message-Id: <20200825002540.3351-14-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20200825002540.3351-1-yu-cheng.yu@intel.com> References: <20200825002540.3351-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: EC46D100E690B X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 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_HW (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 --- v10: -Revise commit log. arch/x86/include/asm/traps.h | 2 ++ arch/x86/mm/fault.c | 19 +++++++++++++++++++ 2 files changed, 21 insertions(+) diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h index 714b1a30e7b0..28b493c53d70 100644 --- a/arch/x86/include/asm/traps.h +++ b/arch/x86/include/asm/traps.h @@ -50,6 +50,7 @@ void __noreturn handle_stack_overflow(const char *message, * 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 */ enum x86_pf_error_code { X86_PF_PROT = 1 << 0, @@ -58,5 +59,6 @@ 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, }; #endif /* _ASM_X86_TRAPS_H */ diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 35f1498e9832..db4018d122ca 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1063,6 +1063,17 @@ 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))) @@ -1197,6 +1208,14 @@ void do_user_addr_fault(struct pt_regs *regs, perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); + /* + * Clearing _PAGE_DIRTY_HW 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 (hw_error_code & X86_PF_SHSTK) + flags |= FAULT_FLAG_WRITE; if (hw_error_code & X86_PF_WRITE) flags |= FAULT_FLAG_WRITE; if (hw_error_code & X86_PF_INSTR)