net: mvpp2: cls: Prevent buffer overflow in mvpp2_ethtool_cls_rule_del()

The "info->fs.location" is a u32 that comes from the user via the
ethtool_set_rxnfc() function.  We need to check for invalid values to
prevent a buffer overflow.

I copy and pasted this check from the mvpp2_ethtool_cls_rule_ins()
function.

Fixes: 90b509b3 ("net: mvpp2: cls: Add Classification offload support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/mvpp2/mvpp2_cls.c

@@ -1428,6 +1428,9 @@ int mvpp2_ethtool_cls_rule_del(struct mvpp2_port *port,
 	struct mvpp2_ethtool_fs *efs;
 	int ret;
 
+	if (info->fs.location >= MVPP2_N_RFS_ENTRIES_PER_FLOW)
+		return -EINVAL;
+
 	efs = port->rfs_rules[info->fs.location];
 	if (!efs)
 		return -EINVAL;