From patchwork Fri May 15 00:43:53 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jarkko Sakkinen X-Patchwork-Id: 11550155 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 D87DE90 for ; Fri, 15 May 2020 00:44:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CA2FF20709 for ; Fri, 15 May 2020 00:44:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728115AbgEOAo6 (ORCPT ); Thu, 14 May 2020 20:44:58 -0400 Received: from mga04.intel.com ([192.55.52.120]:44523 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726170AbgEOAo6 (ORCPT ); Thu, 14 May 2020 20:44:58 -0400 IronPort-SDR: DyCgFEJaKqGukVPcxCuEzhdRhnUE76O75NjaE7wIjdYkKvL8nirC2mxj0ti/KpA4r2/tjEouou v6dLpKUZlDVw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 May 2020 17:44:57 -0700 IronPort-SDR: s6iHDImsjLSYHChwZ5BV/4NM0QkIML2ty4obgfc6TsSj0EHYpDxif68VVzx6OL33YHsJYx+anL /eZrqoDe0efA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,393,1583222400"; d="scan'208";a="253644035" Received: from ashadrin-mobl1.ccr.corp.intel.com (HELO localhost) ([10.249.38.112]) by fmsmga008.fm.intel.com with ESMTP; 14 May 2020 17:44:49 -0700 From: Jarkko Sakkinen To: linux-kernel@vger.kernel.org, x86@kernel.org, linux-sgx@vger.kernel.org Cc: akpm@linux-foundation.org, dave.hansen@intel.com, sean.j.christopherson@intel.com, nhorman@redhat.com, npmccallum@redhat.com, haitao.huang@intel.com, andriy.shevchenko@linux.intel.com, tglx@linutronix.de, kai.svahn@intel.com, bp@alien8.de, josh@joshtriplett.org, luto@kernel.org, kai.huang@intel.com, rientjes@google.com, cedric.xing@intel.com, puiterwijk@redhat.com, Jethro Beekman , Jarkko Sakkinen Subject: [PATCH v30 03/20] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Date: Fri, 15 May 2020 03:43:53 +0300 Message-Id: <20200515004410.723949-4-jarkko.sakkinen@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200515004410.723949-1-jarkko.sakkinen@linux.intel.com> References: <20200515004410.723949-1-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 bit 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 react when this happens (e.g. rec-create the enclave, which was invalidated). [1] Intel SDM: 36.5.1 Enclave Page Cache Map (EPCM) Signed-off-by: Sean Christopherson Acked-by: Jethro Beekman Signed-off-by: Jarkko Sakkinen --- arch/x86/include/asm/traps.h | 1 + arch/x86/mm/fault.c | 13 +++++++++++++ 2 files changed, 14 insertions(+) diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h index c26a7e1d8a2c..07dd9f74d65a 100644 --- a/arch/x86/include/asm/traps.h +++ b/arch/x86/include/asm/traps.h @@ -171,5 +171,6 @@ 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 a51df516b87b..16c53c874bb9 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1201,6 +1201,19 @@ 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