From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934364Ab2AJXEE (ORCPT ); Tue, 10 Jan 2012 18:04:04 -0500 Received: from cantor2.suse.de ([195.135.220.15]:52869 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934168Ab2AJXD4 (ORCPT ); Tue, 10 Jan 2012 18:03:56 -0500 X-Mailbox-Line: From gregkh@clark.kroah.org Tue Jan 10 13:56:05 2012 Message-Id: <20120110215605.730705023@clark.kroah.org> User-Agent: quilt/0.50-25.1 Date: Tue, 10 Jan 2012 13:55:51 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, jhovold@gmail.com, linux-usb@vger.kernel.org, Thilo-Alexander Ginkel Subject: [48/49] usb: cdc-acm: Fix acm_tty_hangup() vs. acm_tty_close() race In-Reply-To: <20120110215609.GA22505@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thilo-Alexander Ginkel [Not upstream as it was fixed differently for 3.3 with a much more "intrusive" rework of the driver - gregkh] There is a race condition involving acm_tty_hangup() and acm_tty_close() where hangup() would attempt to access tty->driver_data without proper locking and NULL checking after close() has potentially already set it to NULL. One possibility to (sporadically) trigger this behavior is to perform a suspend/resume cycle with a running WWAN data connection. This patch addresses the issue by introducing a NULL check for tty->driver_data in acm_tty_hangup() protected by open_mutex and exiting gracefully when hangup() is invoked on a device that has already been closed. Signed-off-by: Thilo-Alexander Ginkel Signed-off-by: Greg Kroah-Hartman --- drivers/usb/class/cdc-acm.c | 12 ++++++++++-- 1 files changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index a8078d0..97f2e58 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -554,10 +554,18 @@ static void acm_port_down(struct acm *acm) static void acm_tty_hangup(struct tty_struct *tty) { - struct acm *acm = tty->driver_data; - tty_port_hangup(&acm->port); + struct acm *acm; + mutex_lock(&open_mutex); + acm = tty->driver_data; + + if (!acm) + goto out; + + tty_port_hangup(&acm->port); acm_port_down(acm); + +out: mutex_unlock(&open_mutex); } -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html