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=unavailable 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 C39A5C4741F for ; Mon, 9 Nov 2020 11:23:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 72DFB206A4 for ; Mon, 9 Nov 2020 11:23:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="0Vjh0sAq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729691AbgKILXK (ORCPT ); Mon, 9 Nov 2020 06:23:10 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:41030 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729650AbgKILXI (ORCPT ); Mon, 9 Nov 2020 06:23:08 -0500 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0A9BFBJ9114136; Mon, 9 Nov 2020 11:22:35 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=0Vjh0sAqfz3IIXX0w2Qj2+/z2AJNBJIT6iE2askMIXeMdQ3KMv/pne/arJMJgNws+Aw0 1nS+l8A0pjDXknU6KjCFhkKFC6yCQxcLCePjNYArKvE7y0hdvzRDqxCxgJLTx2IEvi80 m+2xyv1xHwWfzZVZbMl4Cc97L7/Q6JS7ViGSdgCYgjE2+fnr2mPNdKA15oKXWvgfE+CY EIUwNq6QYU1IGr1RfdcM9w26pQErnKhvUPFJidsP8JuI87azztUbaMXzpE+GgOS+phYG 2fx248gPzcw9sVbYWYI+7/jV0cqpVwegurDok85VNXcZWQpqKSt4FwD0fj7b101ByMlO 4w== Received: from userp3030.oracle.com (userp3030.oracle.com [156.151.31.80]) by userp2120.oracle.com with ESMTP id 34p72ebk5e-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 09 Nov 2020 11:22:35 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0A9BK5fI116644; Mon, 9 Nov 2020 11:22:34 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3030.oracle.com with ESMTP id 34p5gv4xpb-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 09 Nov 2020 11:22:34 +0000 Received: from abhmp0018.oracle.com (abhmp0018.oracle.com [141.146.116.24]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 0A9BMWl9021880; Mon, 9 Nov 2020 11:22:32 GMT Received: from linux.home (/92.157.91.83) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 09 Nov 2020 03:22:32 -0800 From: Alexandre Chartre To: "tglx@linutronix.de"@userv0122.oracle.com, "mingo@redhat.com"@userv0122.oracle.com, "bp@alien8.de"@userv0122.oracle.com, "hpa@zytor.com"@userv0122.oracle.com, "x86@kernel.org"@userv0122.oracle.com, "dave.hansen@linux.intel.com"@userv0122.oracle.com, "luto@kernel.org"@userv0122.oracle.com, "peterz@infradead.org"@userv0122.oracle.com, "linux-kernel@vger.kernel.org"@userv0122.oracle.com, "thomas.lendacky@amd.com"@userv0122.oracle.com, "jroedel@suse.de"@userv0122.oracle.com Cc: "konrad.wilk@oracle.com"@userv0122.oracle.com, "jan.setjeeilers@oracle.com"@userv0122.oracle.com, "junaids@google.com"@userv0122.oracle.com, "oweisse@google.com"@userv0122.oracle.com, "rppt@linux.vnet.ibm.com"@userv0122.oracle.com, "graf@amazon.de"@userv0122.oracle.com, "mgross@linux.intel.com"@userv0122.oracle.com, "kuzuno@gmail.com"@userv0122.oracle.com, "alexandre.chartre@oracle.com"@userv0122.oracle.com Subject: [RFC][PATCH 20/24] x86/pti: Execute NMI handler on the kernel stack Date: Mon, 9 Nov 2020 12:23:15 +0100 Message-Id: <20201109112319.264511-21-alexandre.chartre@oracle.com> X-Mailer: git-send-email 2.18.4 In-Reply-To: <20201109112319.264511-1-alexandre.chartre@oracle.com> References: <20201109112319.264511-1-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 bulkscore=0 mlxlogscore=999 mlxscore=0 spamscore=0 phishscore=0 adultscore=0 malwarescore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011090075 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9799 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 mlxlogscore=999 mlxscore=0 malwarescore=0 suspectscore=0 lowpriorityscore=0 adultscore=0 phishscore=0 priorityscore=1501 spamscore=0 impostorscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011090074 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