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| author | Amit Shah <amit.shah@redhat.com> | 2013-07-29 14:16:13 +0930 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-08-14 22:57:06 -0700 |
| commit | d0bfaacabec9c87b739c31662eaa96af0d1b404c (patch) | |
| tree | ac6efba33bc2cfb70298c65f3e0154fcd0ef7935 | |
| parent | b9ea0ce26ce42ee37891ede0ff6c0162005d53cb (diff) | |
| download | lwn-d0bfaacabec9c87b739c31662eaa96af0d1b404c.tar.gz lwn-d0bfaacabec9c87b739c31662eaa96af0d1b404c.zip | |
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 <mguzik@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/char/virtio_console.c | 13 |
1 files changed, 6 insertions, 7 deletions
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index f77e341631d7..1e10b8b4e453 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -256,9 +256,12 @@ 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); @@ -789,14 +792,10 @@ 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 |