From patchwork Fri Sep 11 12:39:58 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jarkko Sakkinen X-Patchwork-Id: 11771105 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 044181580 for ; Fri, 11 Sep 2020 17:42:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E037F221EF for ; Fri, 11 Sep 2020 17:42:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725978AbgIKRlq (ORCPT ); Fri, 11 Sep 2020 13:41:46 -0400 Received: from mga14.intel.com ([192.55.52.115]:31630 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725849AbgIKMlY (ORCPT ); Fri, 11 Sep 2020 08:41:24 -0400 IronPort-SDR: iu26PoetoOB5GueY7pE/Crh9BH4aXeWaf7WdagiZXPnu3Auih+RmNoEDoeiUxcjLzziOIxw5Sb FO0TPk/+G0Vw== X-IronPort-AV: E=McAfee;i="6000,8403,9740"; a="158028257" X-IronPort-AV: E=Sophos;i="5.76,415,1592895600"; d="scan'208";a="158028257" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Sep 2020 05:41:24 -0700 IronPort-SDR: uTCV9atx4FWbM1OvxA0eRMPcNR4N1DglbTutIbsMGYECW9Eeo1bDtnsbdBpoh81fFcHcC0FgO1 JwDG110hxPUQ== X-IronPort-AV: E=Sophos;i="5.76,415,1592895600"; d="scan'208";a="378551995" Received: from amaksymi-mobl.ger.corp.intel.com (HELO localhost) ([10.252.60.247]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Sep 2020 05:41:10 -0700 From: Jarkko Sakkinen To: x86@kernel.org, linux-sgx@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Sean Christopherson , Jethro Beekman , Darren Kenny , Borislav Petkov , Jarkko Sakkinen , akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com, asapek@google.com, bp@alien8.de, cedric.xing@intel.com, chenalexchen@google.com, conradparker@google.com, cyhanish@google.com, dave.hansen@intel.com, haitao.huang@intel.com, josh@joshtriplett.org, kai.huang@intel.com, kai.svahn@intel.com, kmoy@google.com, ludloff@google.com, luto@kernel.org, nhorman@redhat.com, npmccallum@redhat.com, puiterwijk@redhat.com, rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com Subject: [PATCH v37 03/24] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Date: Fri, 11 Sep 2020 15:39:58 +0300 Message-Id: <20200911124019.42178-4-jarkko.sakkinen@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200911124019.42178-1-jarkko.sakkinen@linux.intel.com> References: <20200911124019.42178-1-jarkko.sakkinen@linux.intel.com> MIME-Version: 1.0 Sender: linux-sgx-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org From: Sean Christopherson Include SGX bit to the PF error codes and throw SIGSEGV with PF_SGX when a #PF with SGX set happens. CPU throws a #PF with the SGX set in the event of Enclave Page Cache Map (EPCM) conflict. The EPCM is a CPU-internal table, which describes the properties for a enclave page. Enclaves are measured and signed software entities, which SGX hosts. [1] Although the primary purpose of the EPCM conflict checks is to prevent malicious accesses to an enclave, an illegit access can happen also for legit reasons. All SGX reserved memory, including EPCM is encrypted with a transient key that does not survive from the power transition. Throwing a SIGSEGV allows user space software to react when this happens (e.g. recreate the enclave, which was invalidated). [1] Intel SDM: 36.5.1 Enclave Page Cache Map (EPCM) Acked-by: Jethro Beekman Reviewed-by: Darren Kenny Reviewed-by: Borislav Petkov Signed-off-by: Sean Christopherson Signed-off-by: Jarkko Sakkinen --- arch/x86/include/asm/traps.h | 14 ++++++++------ arch/x86/mm/fault.c | 13 +++++++++++++ 2 files changed, 21 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h index 714b1a30e7b0..4446f95ad997 100644 --- a/arch/x86/include/asm/traps.h +++ b/arch/x86/include/asm/traps.h @@ -44,12 +44,13 @@ void __noreturn handle_stack_overflow(const char *message, /* * Page fault error code bits: * - * bit 0 == 0: no page found 1: protection fault - * bit 1 == 0: read access 1: write access - * bit 2 == 0: kernel-mode access 1: user-mode access - * bit 3 == 1: use of reserved bit detected - * bit 4 == 1: fault was an instruction fetch - * bit 5 == 1: protection keys block access + * bit 0 == 0: no page found 1: protection fault + * bit 1 == 0: read access 1: write access + * bit 2 == 0: kernel-mode access 1: user-mode access + * bit 3 == 1: use of reserved bit detected + * bit 4 == 1: fault was an instruction fetch + * bit 5 == 1: protection keys block access + * bit 15 == 1: inside SGX enclave */ 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_SGX = 1 << 15, }; #endif /* _ASM_X86_TRAPS_H */ diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 35f1498e9832..1a7cc6d3281a 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1054,6 +1054,19 @@ access_error(unsigned long error_code, struct vm_area_struct *vma) if (error_code & X86_PF_PK) return 1; + /* + * Access is blocked by the Enclave Page Cache Map (EPCM), i.e. the + * access is allowed by the PTE but not the EPCM. This usually happens + * when the EPCM is yanked out from under us, e.g. by hardware after a + * suspend/resume cycle. In any case, software, i.e. the kernel, can't + * fix the source of the fault as the EPCM can't be directly modified by + * software. Handle the fault as an access error in order to signal + * userspace so that userspace can rebuild their enclave(s), even though + * userspace may not have actually violated access permissions. + */ + if (unlikely(error_code & X86_PF_SGX)) + return 1; + /* * Make sure to check the VMA so that we do not perform * faults just to hit a X86_PF_PK as soon as we fill in a