staging: slicoss: fix use-after-free bug in slic_entry_remove

This patch fixes a use-after-free bug that causes a null pointer
dereference in slic_entry_halt.

Since unregister_netdev() will ultimately call slic_entry_halt (the
net_device ndo_stop() virtual function for this device), we should
call it before freeing the memory used by slic_entry_halt.
Signed-off-by: David Matlack <dmatlack@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/slicoss/slicoss.c

@@ -2525,9 +2525,10 @@ static void slic_entry_remove(struct pci_dev *pcidev)
 	struct sliccard *card;
 	struct mcast_address *mcaddr, *mlist;
 
+	unregister_netdev(dev);
+
 	slic_adapter_freeresources(adapter);
 	slic_unmap_mmio_space(adapter);
-	unregister_netdev(dev);
 
 	/* free multicast addresses */
 	mlist = adapter->mcastaddrs;