From patchwork Mon Jun 1 07:52:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jarkko Sakkinen X-Patchwork-Id: 11581641 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 4DBAB139A for ; Mon, 1 Jun 2020 07:52:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3A6862074B for ; Mon, 1 Jun 2020 07:52:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728207AbgFAHwu (ORCPT ); Mon, 1 Jun 2020 03:52:50 -0400 Received: from mga12.intel.com ([192.55.52.136]:20495 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725999AbgFAHwu (ORCPT ); Mon, 1 Jun 2020 03:52:50 -0400 IronPort-SDR: +/L0KEGg4+JmYihYS9Hp4kQzfqXZdSCBF2DJBKhiEKbvD5v8elbV6cO8Pd2+NWpQ4+qWEOoPBs ai4gFFf8ZlOQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Jun 2020 00:52:50 -0700 IronPort-SDR: ZENFADukCaAAbiwEpdQOQCnE+MWwKzsbRYO4s48SXz4WquW1XJ+3jTtQvL4NxYpt133NGqC9Pl BIlmedTwh7BQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,460,1583222400"; d="scan'208";a="311879489" Received: from yhanin-mobl1.ger.corp.intel.com (HELO localhost) ([10.249.43.17]) by FMSMGA003.fm.intel.com with ESMTP; 01 Jun 2020 00:52:44 -0700 From: Jarkko Sakkinen To: linux-kernel@vger.kernel.org, x86@kernel.org, linux-sgx@vger.kernel.org Cc: Sean Christopherson , Jethro Beekman , 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 v32 03/21] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Date: Mon, 1 Jun 2020 10:52:00 +0300 Message-Id: <20200601075218.65618-4-jarkko.sakkinen@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200601075218.65618-1-jarkko.sakkinen@linux.intel.com> References: <20200601075218.65618-1-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) Acked-by: Jethro Beekman Signed-off-by: Sean Christopherson 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