usb: serial: prevent suspend/resume from racing against probe/remove

Some usb-serial drivers may access port data in their suspend/
resume functions. Such drivers must always verify the validity
of the data as both suspend and resume can be called both before
usb_serial_device_probe and after usb_serial_device_remove.

But the port data may be invalidated during port_probe and
port_remove. This patch prevents the race against suspend and
resume by disabling suspend while port_probe or port_remove is
running.

Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/serial/bus.c b/drivers/usb/serial/bus.c
index f398d1e..c15f2e7 100644 (file)
--- a/drivers/usb/serial/bus.c
+++ b/drivers/usb/serial/bus.c
@@ -61,18 +61,23 @@ static int usb_serial_device_probe(struct device *dev)
                goto exit;
        }
 
+       /* make sure suspend/resume doesn't race against port_probe */
+       retval = usb_autopm_get_interface(port->serial->interface);
+       if (retval)
+               goto exit;
+
        driver = port->serial->type;
        if (driver->port_probe) {
                retval = driver->port_probe(port);
                if (retval)
-                       goto exit;
+                       goto exit_with_autopm;
        }
 
        retval = device_create_file(dev, &dev_attr_port_number);
        if (retval) {
                if (driver->port_remove)
                        retval = driver->port_remove(port);
-               goto exit;
+               goto exit_with_autopm;
        }
 
        minor = port->number;
@@ -81,6 +86,8 @@ static int usb_serial_device_probe(struct device *dev)
                 "%s converter now attached to ttyUSB%d\n",
                 driver->description, minor);
 
+exit_with_autopm:
+       usb_autopm_put_interface(port->serial->interface);
 exit:
        return retval;
 }
@@ -96,6 +103,9 @@ static int usb_serial_device_remove(struct device *dev)
        if (!port)
                return -ENODEV;
 
+       /* make sure suspend/resume doesn't race against port_remove */
+       usb_autopm_get_interface(port->serial->interface);
+
        device_remove_file(&port->dev, &dev_attr_port_number);
 
        driver = port->serial->type;
@@ -107,6 +117,7 @@ static int usb_serial_device_remove(struct device *dev)
        dev_info(dev, "%s converter now disconnected from ttyUSB%d\n",
                 driver->description, minor);
 
+       usb_autopm_put_interface(port->serial->interface);
        return retval;
 }