usbip:vudc: BUG kmalloc-2048 (Not tainted): Poison overwritten

In rmmod path, usbip_vudc does platform_device_put() twice once from
platform_device_unregister() and then from put_vudc_device().

The second put results in:

BUG kmalloc-2048 (Not tainted): Poison overwritten error or
BUG: KASAN: use-after-free in kobject_put+0x1e/0x230 if KASAN is
enabled.

[  169.042156] calling  init+0x0/0x1000 [usbip_vudc] @ 1697
[  169.042396] =============================================================================
[  169.043678] probe of usbip-vudc.0 returned 1 after 350 usecs
[  169.044508] BUG kmalloc-2048 (Not tainted): Poison overwritten
[  169.044509] -----------------------------------------------------------------------------
...
[  169.057849] INFO: Freed in device_release+0x2b/0x80 age=4223 cpu=3 pid=1693
[  169.057852] 	kobject_put+0x86/0x1b0
[  169.057853] 	0xffffffffc0c30a96
[  169.057855] 	__x64_sys_delete_module+0x157/0x240

Fix it to call platform_device_del() instead and let put_vudc_device() do
the platform_device_put().
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/usbip/vudc_main.c

@@ -73,6 +73,10 @@ static int __init init(void)
 cleanup:
 	list_for_each_entry_safe(udc_dev, udc_dev2, &vudc_devices, dev_entry) {
 		list_del(&udc_dev->dev_entry);
+		/*
+		 * Just do platform_device_del() here, put_vudc_device()
+		 * calls the platform_device_put()
+		 */
 		platform_device_del(udc_dev->pdev);
 		put_vudc_device(udc_dev);
 	}
@@ -89,7 +93,11 @@ static void __exit cleanup(void)
 
 	list_for_each_entry_safe(udc_dev, udc_dev2, &vudc_devices, dev_entry) {
 		list_del(&udc_dev->dev_entry);
-		platform_device_unregister(udc_dev->pdev);
+		/*
+		 * Just do platform_device_del() here, put_vudc_device()
+		 * calls the platform_device_put()
+		 */
+		platform_device_del(udc_dev->pdev);
 		put_vudc_device(udc_dev);
 	}
 	platform_driver_unregister(&vudc_driver);