From patchwork Tue Sep 15 11:28:21 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jarkko Sakkinen X-Patchwork-Id: 11778627 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 EFC236CA for ; Wed, 16 Sep 2020 00:55:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D2AF220BED for ; Wed, 16 Sep 2020 00:55:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=kapsi.fi header.i=@kapsi.fi header.b="h5Sm96yr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726355AbgIPAzZ (ORCPT ); Tue, 15 Sep 2020 20:55:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34640 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726186AbgIOLbl (ORCPT ); Tue, 15 Sep 2020 07:31:41 -0400 Received: from mail.kapsi.fi (mail.kapsi.fi [IPv6:2001:67c:1be8::25]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A9BACC061352; Tue, 15 Sep 2020 04:28:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=kapsi.fi; s=20161220; h=Content-Transfer-Encoding:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=Z0z7VU0ZJOglP2ZP2H14DlOIQchhVanxR/WdYj/tOzs=; b=h5Sm96yr/Qkruup+epes08udyz r711H3ZgLbXQYcVTRyagzEigr7rNiDloZsW8Jnp17rJUfjID/XyohmHSgi9rsyHYQbJlgMg/Ks2Wj ciADLkcMjwnDv4Ax+65xS11vtEEuA+KjqqoAfVa5HVHS3lWF5K1keYA0gZzQSJw3mKdDy/9XKUxpA taWpU9ugwPYc4K9NU+gRPg+KXks184u44BaxWNVhpRm2CnvJDhPUSbzeUGHCQMw9TWerJy/325Snx p7O5DUQO8nFsiBS4ovD+THijDUDX74I80Il6Y3M1d8Ke6wCq1zluAEmDp5bNVvrRsp2Uze+WfOXi6 wU2wr6Mw==; Received: from 83-245-197-237.elisa-laajakaista.fi ([83.245.197.237] helo=localhost) by mail.kapsi.fi with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1kI98g-0000hp-Vq; Tue, 15 Sep 2020 14:28:47 +0300 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 v38 03/24] x86/mm: x86/sgx: Signal SIGSEGV with PF_SGX Date: Tue, 15 Sep 2020 14:28:21 +0300 Message-Id: <20200915112842.897265-4-jarkko.sakkinen@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200915112842.897265-1-jarkko.sakkinen@linux.intel.com> References: <20200915112842.897265-1-jarkko.sakkinen@linux.intel.com> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 83.245.197.237 X-SA-Exim-Mail-From: jjs@kapsi.fi X-SA-Exim-Scanned: No (on mail.kapsi.fi); SAEximRunCond expanded to false 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