ethtool: Null-terminate filename passed to ethtool_ops::flash_device

commit 786f5281 upstream.

The parameters for ETHTOOL_FLASHDEV include a filename, which ought to
be null-terminated.  Currently the only driver that implements
ethtool_ops::flash_device attempts to add a null terminator if
necessary, but does it wrongly.  Do it in the ethtool core instead.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/ethernet/emulex/benet/be_ethtool.c

@@ -649,12 +649,8 @@ static int
 be_do_flash(struct net_device *netdev, struct ethtool_flash *efl)
 {
 	struct be_adapter *adapter = netdev_priv(netdev);
-	char file_name[ETHTOOL_FLASH_MAX_FILENAME];
 
-	file_name[ETHTOOL_FLASH_MAX_FILENAME - 1] = 0;
-	strcpy(file_name, efl->data);
-
-	return be_load_fw(adapter, file_name);
+	return be_load_fw(adapter, efl->data);
 }
 
 static int

net/core/ethtool.c

@@ -1549,6 +1549,8 @@ static noinline_for_stack int ethtool_flash_device(struct net_device *dev,
 	if (!dev->ethtool_ops->flash_device)
 		return -EOPNOTSUPP;
 
+	efl.data[ETHTOOL_FLASH_MAX_FILENAME - 1] = 0;
+
 	return dev->ethtool_ops->flash_device(dev, &efl);
 }