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>

1 files changed, 13 insertions, 2 deletions

diff --git a/drivers/usb/serial/bus.c b/drivers/usb/serial/bus.c
index f398d1e34474..c15f2e7cefc7 100644
--- 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;
 }