From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754109AbaBZUON (ORCPT ); Wed, 26 Feb 2014 15:14:13 -0500 Received: from cavan.codon.org.uk ([93.93.128.6]:44116 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753725AbaBZULl (ORCPT ); Wed, 26 Feb 2014 15:11:41 -0500 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 05/12] Restrict /dev/mem and /dev/kmem when trusted_kernel is true Date: Wed, 26 Feb 2014 15:11:06 -0500 Message-Id: <1393445473-15068-6-git-send-email-matthew.garrett@nebula.com> X-Mailer: git-send-email 1.8.5.3 In-Reply-To: <1393445473-15068-1-git-send-email-matthew.garrett@nebula.com> References: <1393445473-15068-1-git-send-email-matthew.garrett@nebula.com> X-SA-Do-Not-Run: Yes X-SA-Exim-Connect-IP: 209.6.207.143 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 Allowing users to write to address space provides mechanisms that may permit modification of the kernel at runtime. Prevent this if trusted_kernel is true. Signed-off-by: Matthew Garrett --- drivers/char/mem.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 15331a8..2cecab9 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -158,6 +158,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf, unsigned long copied; void *ptr; + if (get_trusted_kernel()) + return -EPERM; + if (!valid_phys_addr_range(p, count)) return -EFAULT; @@ -496,6 +499,9 @@ static ssize_t write_kmem(struct file *file, const char __user *buf, char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */ int err = 0; + if (get_trusted_kernel()) + return -EPERM; + if (p < (unsigned long) high_memory) { unsigned long to_write = min_t(unsigned long, count, (unsigned long)high_memory - p); -- 1.8.5.3