From 0426ea8291c0cdcf0d585c39a7bfae18e621d93b Mon Sep 17 00:00:00 2001 From: Amit Shah Date: Mon, 29 Jul 2013 14:16:13 +0930 Subject: virtio: console: fix race with port unplug and open/close commit 057b82be3ca3d066478e43b162fc082930a746c9 upstream. 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. Reported-by: Mateusz Guzik Signed-off-by: Amit Shah Signed-off-by: Rusty Russell Signed-off-by: Ben Hutchings --- drivers/char/virtio_console.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) (limited to 'drivers/char') diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index d5ae736..5746a36 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 -- cgit v1.1