Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933435Ab3CRVdq (ORCPT ); Mon, 18 Mar 2013 17:33:46 -0400 Received: from cavan.codon.org.uk ([93.93.128.6]:35950 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933378Ab3CRVdA (ORCPT ); Mon, 18 Mar 2013 17:33:00 -0400 From: Matthew Garrett To: linux-kernel@vger.kernel.org Cc: linux-security-module@vger.kernel.org, linux-efi@vger.kernel.org, kexec@lists.infradead.org, linux-pci@vger.kernel.org, Matthew Garrett Subject: [PATCH 09/12] Require CAP_COMPROMISE_KERNEL for /dev/mem and /dev/kmem access Date: Mon, 18 Mar 2013 17:32:30 -0400 Message-Id: <1363642353-30749-9-git-send-email-matthew.garrett@nebula.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1363642353-30749-1-git-send-email-matthew.garrett@nebula.com> References: <1363642353-30749-1-git-send-email-matthew.garrett@nebula.com> X-SA-Do-Not-Run: Yes X-SA-Exim-Connect-IP: 2001:470:1f07:1371:e0f4:3a1:9c35:d688 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: 1286 Lines: 40 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 7eee4d8..772ee2b 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); -- 1.8.1.2 -- 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/