From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757501Ab3A1Qnf (ORCPT ); Mon, 28 Jan 2013 11:43:35 -0500 Received: from cavan.codon.org.uk ([93.93.128.6]:34045 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757451Ab3A1Qm4 (ORCPT ); Mon, 28 Jan 2013 11:42:56 -0500 From: Matthew Garrett To: linux-kernel@vger.kernel.org Cc: linux-efi@vger.kernel.org, linux-security-module@vger.kernel.org, Matthew Garrett Subject: [PATCH 09/15] Restrict /dev/mem and /dev/kmem in secure boot setups Date: Mon, 28 Jan 2013 11:42:33 -0500 Message-Id: <1359391359-25783-10-git-send-email-matthew.garrett@nebula.com> X-Mailer: git-send-email 1.8.0.2 In-Reply-To: <1359391359-25783-1-git-send-email-matthew.garrett@nebula.com> References: <1359391359-25783-1-git-send-email-matthew.garrett@nebula.com> X-SA-Do-Not-Run: Yes X-SA-Exim-Connect-IP: 2001:470:1f07:1371:6267:20ff:fec3:2318 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 makes it possible for the kernel to be subverted. Restrict this when we need to protect the kernel. 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 fc28099..b5df7a8 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 (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + if (!valid_phys_addr_range(p, count)) return -EFAULT; @@ -530,6 +533,9 @@ 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 (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + if (p < (unsigned long) high_memory) { unsigned long to_write = min_t(unsigned long, count, (unsigned long)high_memory - p); -- 1.8.0.2