From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753852Ab2KQAUY (ORCPT ); Fri, 16 Nov 2012 19:20:24 -0500 Received: from smtp.outflux.net ([198.145.64.163]:54879 "EHLO smtp.outflux.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753687Ab2KQAUX (ORCPT ); Fri, 16 Nov 2012 19:20:23 -0500 Date: Fri, 16 Nov 2012 16:20:16 -0800 From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , ellyjones@chromium.org Subject: [PATCH] devtmpfs: mount with noexec and nosuid Message-ID: <20121117002016.GA13493@www.outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-HELO: www.outflux.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since devtmpfs is writable, make the default noexec nosuid as well. This protects from the case of a privileged process having an arbitrary file write flaw and an argumentless arbitrary execution (i.e. it would lack the ability to run "mount -o remount,exec,suid /dev"), with a system that already has nosuid,noexec on all other writable mounts. Cc: ellyjones@chromium.org Signed-off-by: Kees Cook --- drivers/base/devtmpfs.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c index 147d1a4..b7e2e57 100644 --- a/drivers/base/devtmpfs.c +++ b/drivers/base/devtmpfs.c @@ -340,6 +340,7 @@ static int handle_remove(const char *nodename, struct device *dev) int devtmpfs_mount(const char *mntdir) { int err; + int mflags = MS_SILENT | MS_NOEXEC | MS_NOSUID; if (!mount_dev) return 0; @@ -347,7 +348,7 @@ int devtmpfs_mount(const char *mntdir) if (!thread) return 0; - err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL); + err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", mflags, NULL); if (err) printk(KERN_INFO "devtmpfs: error mounting %i\n", err); else @@ -368,11 +369,12 @@ static int handle(const char *name, umode_t mode, struct device *dev) static int devtmpfsd(void *p) { char options[] = "mode=0755"; + int mflags = MS_SILENT | MS_NOEXEC | MS_NOSUID; int *err = p; *err = sys_unshare(CLONE_NEWNS); if (*err) goto out; - *err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options); + *err = sys_mount("devtmpfs", "/", "devtmpfs", mflags, options); if (*err) goto out; sys_chdir("/.."); /* will traverse into overmounted root */ -- 1.7.9.5 -- Kees Cook Chrome OS Security