epic100: fix use after free on rmmod

commit 8ee9d82 upstream.

epic_close() calls epic_rx() and uses dma buffer, but in epic_remove_one()
we already freed the dma buffer. To fix this issue, reorder function calls
like in the .probe function.

BUG: KASAN: use-after-free in epic_rx+0xa6/0x7e0 [epic100]
Call Trace:
 epic_rx+0xa6/0x7e0 [epic100]
 epic_close+0xec/0x2f0 [epic100]
 unregister_netdev+0x18/0x20
 epic_remove_one+0xaa/0xf0 [epic100]

Fixes: 1da177e ("Linux-2.6.12-rc2")
Reported-by: Yilun Wu <yiluwu@cs.stonybrook.edu>
Signed-off-by: Tong Zhang <ztong0001@gmail.com>
Reviewed-by: Francois Romieu <romieu@fr.zoreil.com>
Link: https://lore.kernel.org/r/20220627043351.25615-1-ztong0001@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/ethernet/smsc/epic100.c

@@ -1513,14 +1513,14 @@ static void epic_remove_one(struct pci_dev *pdev)
 	struct net_device *dev = pci_get_drvdata(pdev);
 	struct epic_private *ep = netdev_priv(dev);
 
+	unregister_netdev(dev);
 	dma_free_coherent(&pdev->dev, TX_TOTAL_SIZE, ep->tx_ring,
 			  ep->tx_ring_dma);
 	dma_free_coherent(&pdev->dev, RX_TOTAL_SIZE, ep->rx_ring,
 			  ep->rx_ring_dma);
-	unregister_netdev(dev);
 	pci_iounmap(pdev, ep->ioaddr);
-	pci_release_regions(pdev);
 	free_netdev(dev);
+	pci_release_regions(pdev);
 	pci_disable_device(pdev);
 	/* pci_power_off(pdev, -1); */
 }