USB: legousbtower: fix open after failed reset request

BugLink: https://bugs.launchpad.net/bugs/1848780

commit 0b074f69 upstream.

The driver would return with a nonzero open count in case the reset
control request failed. This would prevent any further attempts to open
the char dev until the device was disconnected.

Fix this by incrementing the open count only on successful open.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Johan Hovold <johan@kernel.org>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20190919083039.30898-5-johan@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/usb/misc/legousbtower.c

@@ -354,7 +354,6 @@ static int tower_open (struct inode *inode, struct file *file)
 		retval = -EBUSY;
 		goto unlock_exit;
 	}
-	dev->open_count = 1;
 
 	/* reset the tower */
 	result = usb_control_msg (dev->udev,
@@ -394,13 +393,14 @@ static int tower_open (struct inode *inode, struct file *file)
 		dev_err(&dev->udev->dev,
 			"Couldn't submit interrupt_in_urb %d\n", retval);
 		dev->interrupt_in_running = 0;
-		dev->open_count = 0;
 		goto unlock_exit;
 	}
 
 	/* save device in the file's private structure */
 	file->private_data = dev;
 
+	dev->open_count = 1;
+
 unlock_exit:
 	mutex_unlock(&dev->lock);