[PATCHv3 1/4] rio500: refuse more than one device at a time

[Oliver Neukum <oneukum@xxxxxxxx>]

This driver is using a global variable. It cannot handle more than
one device at a time. The issue has been existing since the dawn
of the driver.

V2: Fixed locking in probe()
    Fixed Documentation
V3: Fixed formatting of Documentation

Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
Reported-by: syzbot+35f04d136fc975a70da4@xxxxxxxxxxxxxxxxxxxxxxxxx
---
 drivers/usb/misc/rio500.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/misc/rio500.c b/drivers/usb/misc/rio500.c
index 13e4889bc34f..fa921ae60ffa 100644
--- a/drivers/usb/misc/rio500.c
+++ b/drivers/usb/misc/rio500.c
@@ -447,15 +447,23 @@ static int probe_rio(struct usb_interface *intf,
 {
 	struct usb_device *dev = interface_to_usbdev(intf);
 	struct rio_usb_data *rio = &rio_instance;
-	int retval;
+	int retval = 0;
 
-	dev_info(&intf->dev, "USB Rio found at address %d\n", dev->devnum);
+	mutex_lock(&rio500_mutex);
+	if (rio->present) {
+		dev_info(&intf->dev, "Second USB Rio at address %d refused\n", dev->devnum);
+		retval = -EBUSY;
+		goto bail_out;
+	} else {
+		dev_info(&intf->dev, "USB Rio found at address %d\n", dev->devnum);
+	}
 
 	retval = usb_register_dev(intf, &usb_rio_class);
 	if (retval) {
 		dev_err(&dev->dev,
 			"Not able to get a minor for this device.\n");
-		return -ENOMEM;
+		retval = -ENOMEM;
+		goto bail_out;
 	}
 
 	rio->rio_dev = dev;
@@ -464,7 +472,8 @@ static int probe_rio(struct usb_interface *intf,
 		dev_err(&dev->dev,
 			"probe_rio: Not enough memory for the output buffer\n");
 		usb_deregister_dev(intf, &usb_rio_class);
-		return -ENOMEM;
+		retval = -ENOMEM;
+		goto bail_out;
 	}
 	dev_dbg(&intf->dev, "obuf address:%p\n", rio->obuf);
 
@@ -473,7 +482,8 @@ static int probe_rio(struct usb_interface *intf,
 			"probe_rio: Not enough memory for the input buffer\n");
 		usb_deregister_dev(intf, &usb_rio_class);
 		kfree(rio->obuf);
-		return -ENOMEM;
+		retval = -ENOMEM;
+		goto bail_out;
 	}
 	dev_dbg(&intf->dev, "ibuf address:%p\n", rio->ibuf);
 
@@ -481,8 +491,10 @@ static int probe_rio(struct usb_interface *intf,
 
 	usb_set_intfdata (intf, rio);
 	rio->present = 1;
+bail_out:
+	mutex_unlock(&rio500_mutex);
 
-	return 0;
+	return retval;
 }
 
 static void disconnect_rio(struct usb_interface *intf)
-- 
2.16.4