Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754859Ab3IIQBI (ORCPT ); Mon, 9 Sep 2013 12:01:08 -0400 Received: from cavan.codon.org.uk ([93.93.128.6]:45188 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751409Ab3IIQBF (ORCPT ); Mon, 9 Sep 2013 12:01:05 -0400 From: Matthew Garrett To: linux-kernel@vger.kernel.org Cc: keescook@chromium.org, gregkh@linuxfoundation.org, hpa@zytor.com, linux-efi@vger.kernel.org, jmorris@namei.org, linux-security-module@vger.kernel.org, Matthew Garrett Subject: [PATCH 10/12] x86: Restrict MSR access when securelevel is set Date: Mon, 9 Sep 2013 11:49:44 -0400 Message-Id: <1378741786-18430-11-git-send-email-matthew.garrett@nebula.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1378741786-18430-1-git-send-email-matthew.garrett@nebula.com> References: <1378741786-18430-1-git-send-email-matthew.garrett@nebula.com> X-SA-Do-Not-Run: Yes X-SA-Exim-Connect-IP: 2001:470:1f07:1371:5d52:9ee3:3e84:6668 X-SA-Exim-Mail-From: matthew.garrett@nebula.com X-SA-Exim-Scanned: No (on cavan.codon.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1427 Lines: 51 Permitting write access to MSRs allows userspace to modify the running kernel. Prevent this if securelevel has been set. 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 88458fa..6b6cb4f 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -37,6 +37,7 @@ #include #include #include +#include #include #include @@ -103,6 +104,9 @@ static ssize_t msr_write(struct file *file, const char __user *buf, int err = 0; ssize_t bytes = 0; + if (get_securelevel() > 0) + return -EPERM; + if (count % 8) return -EINVAL; /* Invalid chunk size */ @@ -150,6 +154,10 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg) err = -EBADF; break; } + if (get_securelevel() > 0) { + err = -EPERM; + break; + } if (copy_from_user(®s, uregs, sizeof regs)) { err = -EFAULT; break; -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/