From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964914Ab3CZQSP (ORCPT ); Tue, 26 Mar 2013 12:18:15 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:53564 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964834Ab3CZPVx (ORCPT ); Tue, 26 Mar 2013 11:21:53 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Jiri Slaby , Mauro Carvalho Chehab , Bryan Mason , Greg Kroah-Hartman , Luis Henriques Subject: [PATCH 021/150] TTY: do not reset master's packet mode Date: Tue, 26 Mar 2013 15:18:40 +0000 Message-Id: <1364311249-14454-22-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1364311249-14454-1-git-send-email-luis.henriques@canonical.com> References: <1364311249-14454-1-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 3.5.7.9 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiri Slaby commit b81273a132177edd806476b953f6afeb17b786d5 upstream. Now that login from util-linux is forced to drop all references to a TTY which it wants to hangup (to reach reference count 1) we are seeing issues with telnet. When login closes its last reference to the slave PTY, it also resets packet mode on the *master* side. And we have a race here. What telnet does is fork+exec of `login'. Then there are two scenarios: * `login' closes the slave TTY and resets thus master's packet mode, but even now telnet properly sets the mode, or * `telnetd' sets packet mode on the master, `login' closes the slave TTY and resets master's packet mode. The former case is OK. However the latter happens in much more cases, by the order of magnitude to be precise. So when one tries to login to such a messed telnet setup, they see the following: inux login: ogin incorrect Note the missing first letters -- telnet thinks it is still in the packet mode, so when it receives "linux login" from `login', it considers "l" as the type of the packet and strips it. SuS does not mention how the implementation should behave. Both BSDs I checked (Free and Net) do not reset the flag upon the last close. By this I am resurrecting an old bug, see References. We are hitting it regularly now, i.e. with updated util-linux, ergo login. Here, I am changing a behavior introduced back in 2.1 times. It would better have a long time testing before goes upstream. Signed-off-by: Jiri Slaby Cc: Mauro Carvalho Chehab Cc: Bryan Mason References: https://lkml.org/lkml/2009/11/11/223 References: https://bugzilla.redhat.com/show_bug.cgi?id=504703 References: https://bugzilla.novell.com/show_bug.cgi?id=797042 Signed-off-by: Greg Kroah-Hartman Signed-off-by: Luis Henriques --- drivers/tty/pty.c | 1 - 1 file changed, 1 deletion(-) diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c index 5505ffc..ce53594 100644 --- a/drivers/tty/pty.c +++ b/drivers/tty/pty.c @@ -49,7 +49,6 @@ static void pty_close(struct tty_struct *tty, struct file *filp) tty->packet = 0; if (!tty->link) return; - tty->link->packet = 0; set_bit(TTY_OTHER_CLOSED, &tty->link->flags); wake_up_interruptible(&tty->link->read_wait); wake_up_interruptible(&tty->link->write_wait); -- 1.8.1.2