netfilter: flowtable: Fix flushing of offloaded flows on free

Freeing a flowtable with offloaded flows, the flow are deleted from
hardware but are not deleted from the flow table, leaking them,
and leaving their offload bit on.

Add a second pass of the disabled gc to delete the these flows from
the flow table before freeing it.

Fixes: c29f74e0 ("netfilter: nf_flow_table: hardware offload support")
Signed-off-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_flow_table_core.c

@@ -554,6 +554,9 @@ void nf_flow_table_free(struct nf_flowtable *flow_table)
 	nf_flow_table_iterate(flow_table, nf_flow_table_do_cleanup, NULL);
 	nf_flow_table_iterate(flow_table, nf_flow_offload_gc_step, flow_table);
 	nf_flow_table_offload_flush(flow_table);
+	if (nf_flowtable_hw_offload(flow_table))
+		nf_flow_table_iterate(flow_table, nf_flow_offload_gc_step,
+				      flow_table);
 	rhashtable_destroy(&flow_table->rhashtable);
 }
 EXPORT_SYMBOL_GPL(nf_flow_table_free);