Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754956Ab3IIPw2 (ORCPT ); Mon, 9 Sep 2013 11:52:28 -0400 Received: from cavan.codon.org.uk ([93.93.128.6]:44958 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754531Ab3IIPwJ (ORCPT ); Mon, 9 Sep 2013 11:52:09 -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 05/12] Restrict /dev/mem and /dev/kmem when securelevel is set. Date: Mon, 9 Sep 2013 11:49:39 -0400 Message-Id: <1378741786-18430-6-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: 1283 Lines: 41 Allowing users to write to address space provides mechanisms that may permit modification of the kernel at runtime. Prevent this if securelevel has been set. 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 741f536..91d1cff 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -159,6 +159,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf, unsigned long copied; void *ptr; + if (get_securelevel() > 0) + return -EPERM; + if (!valid_phys_addr_range(p, count)) return -EFAULT; @@ -497,6 +500,9 @@ 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_securelevel() > 0) + return -EPERM; + if (p < (unsigned long) high_memory) { unsigned long to_write = min_t(unsigned long, count, (unsigned long)high_memory - p); -- 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/