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=-12.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,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 3BCFAC388F7 for ; Mon, 9 Nov 2020 14:44:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D718B206E3 for ; Mon, 9 Nov 2020 14:44:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="YuDMQdv7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731980AbgKIOoE (ORCPT ); Mon, 9 Nov 2020 09:44:04 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:48024 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729854AbgKIOoD (ORCPT ); Mon, 9 Nov 2020 09:44:03 -0500 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0A9EhioX194583; Mon, 9 Nov 2020 14:43:44 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : in-reply-to : references; s=corp-2020-01-29; bh=eHZrLbVYUZh4CLglYJbimy4Cf1h2wuErP22WKC3JKHk=; b=YuDMQdv7oI9Ld8AxbKnmDNB7zvXJDMPe0mxKjeeen2w1Ejkbsrx9lKgjW7JJ6ojpYbd4 kiRiN9iZl82anYG1Bq38MHxjJJohGeOPYapZOMe9yNVrr255x3KDYIkwSJ9KyCWyNIIf 1ebaylIJ2BLZIm5hbJTIBnCsLhsK0dsmk4RUCHovkueIFhNo+lrFd3RJtg2Ykh8MLirn zIBH+UbZIfOqxLPQe+1I5/lyYu/reDj2QnJqnGJ1CitKoYkhuFAjXuuiClEqGCZ6xqzo dAqVjI908/Jyow4AHVYsFkmpzLVTGXpJE2VcrXvCNduJBJo29WOgzmZoqrJETA3S/Qm2 nQ== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by aserp2120.oracle.com with ESMTP id 34nkhkp7ut-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 09 Nov 2020 14:43:44 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0A9EemTn174469; Mon, 9 Nov 2020 14:43:44 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserp3020.oracle.com with ESMTP id 34p5fxs2gw-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 09 Nov 2020 14:43:44 +0000 Received: from abhmp0009.oracle.com (abhmp0009.oracle.com [141.146.116.15]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 0A9EhgUv031931; Mon, 9 Nov 2020 14:43:42 GMT Received: from linux.nl.oracle.com (/10.175.27.128) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 09 Nov 2020 06:43:41 -0800 From: Alexandre Chartre To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org, thomas.lendacky@amd.com, jroedel@suse.de Cc: konrad.wilk@oracle.com, jan.setjeeilers@oracle.com, junaids@google.com, oweisse@google.com, rppt@linux.vnet.ibm.com, graf@amazon.de, mgross@linux.intel.com, kuzuno@gmail.com, alexandre.chartre@oracle.com Subject: [RFC][PATCH 20/24] x86/pti: Execute NMI handler on the kernel stack Date: Mon, 9 Nov 2020 15:44:21 +0100 Message-Id: <20201109144425.270789-21-alexandre.chartre@oracle.com> X-Mailer: git-send-email 2.18.4 In-Reply-To: <20201109144425.270789-1-alexandre.chartre@oracle.com> References: <20201109144425.270789-1-alexandre.chartre@oracle.com> X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9799 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 spamscore=0 malwarescore=0 adultscore=0 phishscore=0 bulkscore=0 mlxlogscore=999 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011090103 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9799 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 priorityscore=1501 mlxscore=0 suspectscore=0 mlxlogscore=999 lowpriorityscore=0 spamscore=0 malwarescore=0 adultscore=0 clxscore=1015 bulkscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011090103 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org After a NMI from userland, the kernel is entered and it switches the stack to the PTI stack which is mapped both in the kernel and in the user page-table. When executing the NMI handler, switch to the kernel stack (which is mapped only in the kernel page-table) so that no kernel data leak to the userland through the stack. Signed-off-by: Alexandre Chartre --- arch/x86/kernel/nmi.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c index 4bc77aaf1303..be0f654c3095 100644 --- a/arch/x86/kernel/nmi.c +++ b/arch/x86/kernel/nmi.c @@ -506,8 +506,18 @@ DEFINE_IDTENTRY_RAW(exc_nmi) inc_irq_stat(__nmi_count); - if (!ignore_nmis) - default_do_nmi(regs); + if (!ignore_nmis) { + if (user_mode(regs)) { + /* + * If we come from userland then we are on the + * trampoline stack, switch to the kernel stack + * to execute the NMI handler. + */ + run_idt(default_do_nmi, regs); + } else { + default_do_nmi(regs); + } + } idtentry_exit_nmi(regs, irq_state); -- 2.18.4