From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932638Ab3EGNky (ORCPT ); Tue, 7 May 2013 09:40:54 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:42152 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932598Ab3EGNku (ORCPT ); Tue, 7 May 2013 09:40:50 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Jiri Slaby , Greg Kroah-Hartman , Luis Henriques Subject: [PATCH 027/118] TTY: do not update atime/mtime on read/write Date: Tue, 7 May 2013 14:37:53 +0100 Message-Id: <1367933964-1564-28-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1367933964-1564-1-git-send-email-luis.henriques@canonical.com> References: <1367933964-1564-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.5.7.12 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiri Slaby commit b0de59b5733d18b0d1974a060860a8b5c1b36a2e upstream. On http://vladz.devzero.fr/013_ptmx-timing.php, we can see how to find out length of a password using timestamps of /dev/ptmx. It is documented in "Timing Analysis of Keystrokes and Timing Attacks on SSH". To avoid that problem, do not update time when reading from/writing to a TTY. I am afraid of regressions as this is a behavior we have since 0.97 and apps may expect the time to be current, e.g. for monitoring whether there was a change on the TTY. Now, there is no change. So this would better have a lot of testing before it goes upstream. References: CVE-2013-0160 Signed-off-by: Jiri Slaby Signed-off-by: Greg Kroah-Hartman Signed-off-by: Luis Henriques --- drivers/tty/tty_io.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index b425c79..e0767b7 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -975,8 +975,7 @@ static ssize_t tty_read(struct file *file, char __user *buf, size_t count, else i = -EIO; tty_ldisc_deref(ld); - if (i > 0) - inode->i_atime = current_fs_time(inode->i_sb); + return i; } @@ -1077,11 +1076,8 @@ static inline ssize_t do_tty_write( break; cond_resched(); } - if (written) { - struct inode *inode = file->f_path.dentry->d_inode; - inode->i_mtime = current_fs_time(inode->i_sb); + if (written) ret = written; - } out: tty_write_unlock(tty); return ret; -- 1.8.1.2