Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933792AbdDERO1 (ORCPT ); Wed, 5 Apr 2017 13:14:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56504 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933748AbdDERMM (ORCPT ); Wed, 5 Apr 2017 13:12:12 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com C298F7D0D5 Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=dhowells@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com C298F7D0D5 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 14/24] x86: Restrict MSR access when the kernel is locked down From: David Howells To: linux-kernel@vger.kernel.org Cc: matthew.garrett@nebula.com, linux-efi@vger.kernel.org, Kees Cook , gnomes@lxorguk.ukuu.org.uk, gregkh@linuxfoundation.org, dhowells@redhat.com, linux-security-module@vger.kernel.org, keyrings@vger.kernel.org Date: Wed, 05 Apr 2017 18:12:04 +0100 Message-ID: <149141232449.31282.15045536717220570492.stgit@warthog.procyon.org.uk> In-Reply-To: <149141219387.31282.6648284836568938717.stgit@warthog.procyon.org.uk> References: <149141219387.31282.6648284836568938717.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Wed, 05 Apr 2017 17:12:07 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1122 Lines: 39 From: Matthew Garrett Writing to MSRs should not be allowed if the kernel is locked down, since it could lead to execution of arbitrary code in kernel mode. Based on a patch by Kees Cook. Cc: Kees Cook Signed-off-by: Matthew Garrett Signed-off-by: David Howells --- arch/x86/kernel/msr.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index ef688804f80d..fbcce028e502 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -84,6 +84,9 @@ static ssize_t msr_write(struct file *file, const char __user *buf, int err = 0; ssize_t bytes = 0; + if (kernel_is_locked_down()) + return -EPERM; + if (count % 8) return -EINVAL; /* Invalid chunk size */ @@ -131,6 +134,10 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg) err = -EBADF; break; } + if (kernel_is_locked_down()) { + err = -EPERM; + break; + } if (copy_from_user(®s, uregs, sizeof regs)) { err = -EFAULT; break;