Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S941381AbcKPVtT (ORCPT ); Wed, 16 Nov 2016 16:49:19 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43364 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935535AbcKPVtO (ORCPT ); Wed, 16 Nov 2016 16:49:14 -0500 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 16/16] x86: Restrict MSR access when the kernel is locked down From: David Howells To: keyrings@vger.kernel.org Cc: matthew.garrett@nebula.com, linux-efi@vger.kernel.org, Kees Cook , linux-kernel@vger.kernel.org, dhowells@redhat.com, linux-security-module@vger.kernel.org Date: Wed, 16 Nov 2016 21:49:12 +0000 Message-ID: <147933295221.19316.10760767173988816147.stgit@warthog.procyon.org.uk> In-Reply-To: <147933283664.19316.12454053022687659937.stgit@warthog.procyon.org.uk> References: <147933283664.19316.12454053022687659937.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 [10.5.110.25]); Wed, 16 Nov 2016 21:49:14 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1304 Lines: 47 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 | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index 7f3550acde1b..b875e54bdbf7 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -39,6 +39,7 @@ #include #include #include +#include #include #include @@ -83,6 +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 */ @@ -130,6 +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;