From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754227AbbCMV5G (ORCPT ); Fri, 13 Mar 2015 17:57:06 -0400 Received: from cavan.codon.org.uk ([93.93.128.6]:32936 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752022AbbCMV5C (ORCPT ); Fri, 13 Mar 2015 17:57:02 -0400 From: Matthew Garrett To: linux-security-module@vger.kernel.org Cc: james.l.morris@oracle.com, serge@hallyn.com, linux-kernel@vger.kernel.org, keescook@chromium.org, hpa@zytor.com, gnomes@lxorguk.ukuu.org.uk, Matthew Garrett Date: Fri, 13 Mar 2015 11:38:26 -1000 Message-Id: <1426282708-21485-11-git-send-email-matthew.garrett@nebula.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1426282708-21485-1-git-send-email-matthew.garrett@nebula.com> References: <1426282708-21485-1-git-send-email-matthew.garrett@nebula.com> X-SA-Do-Not-Run: Yes X-SA-Exim-Connect-IP: 72.253.89.114 X-SA-Exim-Mail-From: matthew.garrett@nebula.com X-Spam-ASN: Subject: [PATCH 10/12] x86: Restrict MSR access when trusted_kernel is true X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:54:46 +0000) X-SA-Exim-Scanned: Yes (on cavan.codon.org.uk) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Permitting write access to MSRs allows userspace to modify the running kernel. Prevent this if trusted_kernel is true. Based on a patch by Kees Cook. Cc: Kees Cook Signed-off-by: Matthew Garrett --- 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 113e707..dec5550 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -39,6 +39,7 @@ #include #include #include +#include #include #include @@ -105,6 +106,9 @@ static ssize_t msr_write(struct file *file, const char __user *buf, int err = 0; ssize_t bytes = 0; + if (get_trusted_kernel()) + return -EPERM; + if (count % 8) return -EINVAL; /* Invalid chunk size */ @@ -152,6 +156,10 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg) err = -EBADF; break; } + if (get_trusted_kernel()) { + err = -EPERM; + break; + } if (copy_from_user(®s, uregs, sizeof regs)) { err = -EFAULT; break; -- 2.1.0