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=-12.7 required=3.0 tests=BAYES_00, 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 ED5ACC388F7 for ; Tue, 10 Nov 2020 16:23:41 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 79A2E20780 for ; Tue, 10 Nov 2020 16:23:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 79A2E20780 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 1E2546B0098; Tue, 10 Nov 2020 11:23:00 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id CB86E6B0099; Tue, 10 Nov 2020 11:22:59 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 90CB86B0096; Tue, 10 Nov 2020 11:22:59 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0249.hostedemail.com [216.40.44.249]) by kanga.kvack.org (Postfix) with ESMTP id DE9ED6B008A for ; Tue, 10 Nov 2020 11:22:58 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 6A5418249980 for ; Tue, 10 Nov 2020 16:22:58 +0000 (UTC) X-FDA: 77469027636.24.fuel72_470747f272f6 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin24.hostedemail.com (Postfix) with ESMTP id 4B4811A4A5 for ; Tue, 10 Nov 2020 16:22:58 +0000 (UTC) X-HE-Tag: fuel72_470747f272f6 X-Filterd-Recvd-Size: 5978 Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by imf30.hostedemail.com (Postfix) with ESMTP for ; Tue, 10 Nov 2020 16:22:57 +0000 (UTC) IronPort-SDR: 8OEjmbretpfaVe32Vv4AfqhLRtv7T7aST7dXI+SyxIf3j4bBegyaD77/GwZxfd0N7OO36ck7jh OG6CmYyj2+JA== X-IronPort-AV: E=McAfee;i="6000,8403,9801"; a="231630863" X-IronPort-AV: E=Sophos;i="5.77,466,1596524400"; d="scan'208";a="231630863" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Nov 2020 08:22:52 -0800 IronPort-SDR: jxit4pkfdtFSwf8JL80U7g+rEwtGKm686zoXKqxe6qVpbqHAYNZ6YLXWAhV0WY770ppuoY+7pf M4hhZE4xcfPQ== X-IronPort-AV: E=Sophos;i="5.77,466,1596524400"; d="scan'208";a="365572858" 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; 10 Nov 2020 08:22:51 -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 v15 13/26] x86/mm: Shadow Stack page fault error checking Date: Tue, 10 Nov 2020 08:21:58 -0800 Message-Id: <20201110162211.9207-14-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20201110162211.9207-1-yu-cheng.yu@intel.com> References: <20201110162211.9207-1-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: Shadow stack accesses are those that are performed by the CPU where it expects to encounter a shadow stack mapping. These accesses are performe= d 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 a= re 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_p= f.h index 305bc1214aef..205766c438b3 100644 --- a/arch/x86/include/asm/trap_pf.h +++ b/arch/x86/include/asm/trap_pf.h @@ -11,6 +11,7 @@ * bit 3 =3D=3D 1: use of reserved bit detected * bit 4 =3D=3D 1: fault was an instruction fetch * bit 5 =3D=3D 1: protection keys block access + * bit 6 =3D=3D 1: shadow stack access fault */ enum x86_pf_error_code { X86_PF_PROT =3D 1 << 0, @@ -19,6 +20,7 @@ enum x86_pf_error_code { X86_PF_RSVD =3D 1 << 3, X86_PF_INSTR =3D 1 << 4, X86_PF_PK =3D 1 << 5, + X86_PF_SHSTK =3D 1 << 6, }; =20 #endif /* _ASM_X86_TRAP_PF_H */ diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 82bf37a5c9ec..941f55ee7c75 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1110,6 +1110,17 @@ access_error(unsigned long error_code, struct vm_a= rea_struct *vma) (error_code & X86_PF_INSTR), foreign)) return 1; =20 + /* + * 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))) @@ -1275,6 +1286,14 @@ void do_user_addr_fault(struct pt_regs *regs, =20 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); =20 + /* + * 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 |=3D FAULT_FLAG_WRITE; if (hw_error_code & X86_PF_WRITE) flags |=3D FAULT_FLAG_WRITE; if (hw_error_code & X86_PF_INSTR) --=20 2.21.0