From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757297AbbCMVjn (ORCPT ); Fri, 13 Mar 2015 17:39:43 -0400 Received: from cavan.codon.org.uk ([93.93.128.6]:60956 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757175AbbCMVjj (ORCPT ); Fri, 13 Mar 2015 17:39:39 -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 11:38:21 -1000 Message-Id: <1426282708-21485-6-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 05/12] Restrict /dev/mem and /dev/kmem 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 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 74227cd..91e7409 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -164,6 +164,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf, unsigned long copied; void *ptr; + if (get_trusted_kernel()) + return -EPERM; + if (p != *ppos) return -EFBIG; @@ -513,6 +516,9 @@ 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); -- 2.1.0