From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756697Ab3IKE7c (ORCPT ); Wed, 11 Sep 2013 00:59:32 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:13847 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754427Ab3IKE5K (ORCPT ); Wed, 11 Sep 2013 00:57:10 -0400 X-Authority-Analysis: v=2.0 cv=V4T/IJbi c=1 sm=0 a=Sro2XwOs0tJUSHxCKfOySw==:17 a=Drc5e87SC40A:10 a=Ciwy3NGCPMMA:10 a=kxAOY3v-hBEA:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=KGjhK52YXX0A:10 a=eWU4qceznocA:10 a=20KFwNOVAAAA:8 a=VwQbUJbxAAAA:8 a=Tty9oNO6AAAA:8 a=5cIBTxRJ4pZzZk2xk6UA:9 a=jEp0ucaQiEUA:10 a=jeBq3FmKZ4MA:10 a=Sro2XwOs0tJUSHxCKfOySw==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 67.255.60.225 Message-Id: <20130911042921.257344440@goodmis.org> User-Agent: quilt/0.60-1 Date: Wed, 11 Sep 2013 00:30:01 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Mateusz Guzik , Amit Shah , Rusty Russell Subject: [174/251] virtio: console: fix race with port unplug and open/close References: <20130911042707.738353451@goodmis.org> Content-Disposition: inline; filename=0174-virtio-console-fix-race-with-port-unplug-and-open-cl.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.6.11.9-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Amit Shah [ Upstream commit 057b82be3ca3d066478e43b162fc082930a746c9 ] There's a window between find_port_by_devt() returning a port and us taking a kref on the port, where the port could get unplugged. Fix it by taking the reference in find_port_by_devt() itself. Problem reported and analyzed by Mateusz Guzik. CC: Reported-by: Mateusz Guzik Signed-off-by: Amit Shah Signed-off-by: Rusty Russell Signed-off-by: Steven Rostedt --- drivers/char/virtio_console.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index d2f7eb0..abca6eb 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -257,9 +257,12 @@ static struct port *find_port_by_devt_in_portdev(struct ports_device *portdev, unsigned long flags; spin_lock_irqsave(&portdev->ports_lock, flags); - list_for_each_entry(port, &portdev->ports, list) - if (port->cdev->dev == dev) + list_for_each_entry(port, &portdev->ports, list) { + if (port->cdev->dev == dev) { + kref_get(&port->kref); goto out; + } + } port = NULL; out: spin_unlock_irqrestore(&portdev->ports_lock, flags); @@ -793,14 +796,10 @@ static int port_fops_open(struct inode *inode, struct file *filp) struct port *port; int ret; + /* We get the port with a kref here */ port = find_port_by_devt(cdev->dev); filp->private_data = port; - /* Prevent against a port getting hot-unplugged at the same time */ - spin_lock_irq(&port->portdev->ports_lock); - kref_get(&port->kref); - spin_unlock_irq(&port->portdev->ports_lock); - /* * Don't allow opening of console port devices -- that's done * via /dev/hvc -- 1.7.10.4