flowcache: Fix resource leaks on namespace exit.

We leak an active timer, the hotcpu notifier and all allocated
resources when we exit a namespace. Fix this by introducing a
flow_cache_fini() function where we release the resources before
we exit.

Fixes: ca925cf1534e ("flowcache: Make flow cache name space aware")
Reported-by: Jakub Kicinski <moorray3@wp.pl>
Tested-by: Jakub Kicinski <moorray3@wp.pl>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Fan Du <fan.du@windriver.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/flow.c b/net/core/flow.c
index 102f8ea..31cfb36 100644
--- a/net/core/flow.c
+++ b/net/core/flow.c
@@ -484,3 +484,22 @@
 	return -ENOMEM;
 }
 EXPORT_SYMBOL(flow_cache_init);
+
+void flow_cache_fini(struct net *net)
+{
+	int i;
+	struct flow_cache *fc = &net->xfrm.flow_cache_global;
+
+	del_timer_sync(&fc->rnd_timer);
+	unregister_hotcpu_notifier(&fc->hotcpu_notifier);
+
+	for_each_possible_cpu(i) {
+		struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, i);
+		kfree(fcp->hash_table);
+		fcp->hash_table = NULL;
+	}
+
+	free_percpu(fc->percpu);
+	fc->percpu = NULL;
+}
+EXPORT_SYMBOL(flow_cache_fini);