[PATCH v2] net: usb: usbnet: fix use-after-free in race on workqueue

[Peter GJ. Park]

When usbnet_disconnect() queued while usbnet_probe() processing,
it results to free_netdev before kevent gets to run on workqueue,
thus workqueue does assign_work() with referencing freeed memory address.

For graceful disconnect and to prevent use-after-free of netdev pointer,
the fix adds canceling work and timer those are placed by usbnet_probe()

Signed-off-by: Peter GJ. Park <gyujoon.park@xxxxxxxxxxx>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
---
 drivers/net/usb/usbnet.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index c04e715a4c2a..3c5d9ba7fa66 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1660,6 +1660,9 @@ void usbnet_disconnect (struct usb_interface *intf)
 	usb_free_urb(dev->interrupt);
 	kfree(dev->padding_pkt);
 
+	timer_delete_sync(&dev->delay);
+	tasklet_kill(&dev->bh);
+	cancel_work_sync(&dev->kevent);
 	free_netdev(net);
 }
 EXPORT_SYMBOL_GPL(usbnet_disconnect);
-- 
2.25.1