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Date: Mon, 12 Aug 2013 23:34:01 -0700 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Mateusz Guzik <mguzik@...hat.com>, Amit Shah <amit.shah@...hat.com>, Rusty Russell <rusty@...tcorp.com.au> Subject: [ 34/60] virtio: console: fix race with port unplug and open/close 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Amit Shah <amit.shah@...hat.com> 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@...hat.com> Signed-off-by: Amit Shah <amit.shah@...hat.com> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- drivers/char/virtio_console.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -272,9 +272,12 @@ static struct port *find_port_by_devt_in 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); @@ -1036,14 +1039,10 @@ static int port_fops_open(struct inode * 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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