From patchwork Tue Apr 14 01:03:03 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 460978 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 441A8140134 for ; Tue, 14 Apr 2015 11:03:49 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754910AbbDNBDR (ORCPT ); Mon, 13 Apr 2015 21:03:17 -0400 Received: from cantor2.suse.de ([195.135.220.15]:51168 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754078AbbDNBDO (ORCPT ); Mon, 13 Apr 2015 21:03:14 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 4B30DABB1; Tue, 14 Apr 2015 01:03:12 +0000 (UTC) Date: Tue, 14 Apr 2015 11:03:03 +1000 From: NeilBrown To: Olivier Sobrie , "David S. Miller" , Jan Dumon Cc: linux-usb@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, GTA04 owners Subject: Re: [PATCH] hso: fix refcnt leak in recent patch. Message-ID: <20150414110303.66edcfee@notabene.brown> In-Reply-To: <20150414093634.4fe24ba3@notabene.brown> References: <20150414093634.4fe24ba3@notabene.brown> X-Mailer: Claws Mail 3.10.1-162-g4d0ed6 (GTK+ 2.24.25; x86_64-suse-linux-gnu) MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, 14 Apr 2015 09:36:34 +1000 NeilBrown wrote: > > > Prior to > commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b > hso: fix crash when device disappears while serial port is open > > hso_serial_open would always kref_get(&serial->parent->ref) before > returning zero. > Since that commit, it only calls kref_get when returning 0 if > serial->port.count was zero. > > This results in calls to > kref_put(&serial->parent->ref, hso_serial_ref_free); > > after hso_serial_ref_free has been called, which dereferences a freed > pointer. > > This patch adds the missing kref_get(). > > Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b > Cc: stable@vger.kernel.org (v4.0) > Cc: Olivier Sobrie > Signed-off-by: NeilBrown > > diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c > index 75befc1bd816..6848fc903340 100644 > --- a/drivers/net/usb/hso.c > +++ b/drivers/net/usb/hso.c > @@ -1299,6 +1299,7 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp) > } > } else { > D1("Port was already open"); > + kref_get(&serial->parent->ref); > } > > usb_autopm_put_interface(serial->parent->interface); Sorry - that was wrong. I'm getting crashes which strongly suggest the kref_put is being called extra times, but I misunderstood the code and was hasty. Maybe this instead? Thanks, NeilBrown From: NeilBrown Date: Tue, 14 Apr 2015 09:33:03 +1000 Subject: [PATCH] hso: fix refcnt leak in recent patch. Prior to commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b hso: fix crash when device disappears while serial port is open a kref_get on serial->parent->ref would be taken on each open, and it would be kref_put on each close. Now the kref_put happens when the tty_struct is finally put (via the 'cleanup') providing tty->driver_data has been set. So the kref_get must be called exact once when tty->driver_data is set. With the current code, if the first open fails the kref_get() is never called, but the kref_put() is called, leaving to a crash. So change the kref_get call to happen exactly when ->driver_data is changed from NULL to non-NULL. Fixes: commit 29bd3bc1194c624ce863cab2a7da9bc1f0c3b47b Cc: stable@vger.kernel.org (v4.0) Cc: Olivier Sobrie Signed-off-by: NeilBrown Tested-by: Olivier Sobrie diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c index 75befc1bd816..17fd3820263a 100644 --- a/drivers/net/usb/hso.c +++ b/drivers/net/usb/hso.c @@ -1278,6 +1278,8 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp) D1("Opening %d", serial->minor); /* setup */ + if (tty->driver_data == NULL) + kref_get(&serial->parent->ref); tty->driver_data = serial; tty_port_tty_set(&serial->port, tty); @@ -1294,8 +1296,6 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp) if (result) { hso_stop_serial_device(serial->parent); serial->port.count--; - } else { - kref_get(&serial->parent->ref); } } else { D1("Port was already open");