Merge branch 'inet-fix-defrag-units-dismantle-races'

Eric Dumazet says:

====================
inet: fix defrag units dismantle races

This series add a new pre_exit() method to struct pernet_operations
to solve a race in defrag units dismantle, without adding extra
delays to netns dismantles.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/inet_frag.h

@@ -20,7 +20,7 @@ struct fqdir {
 
 	/* Keep atomic mem on separate cachelines in structs that include it */
 	atomic_long_t		mem ____cacheline_aligned_in_smp;
-	struct rcu_work		destroy_rwork;
+	struct work_struct	destroy_work;
 };
 
 /**
@@ -113,6 +113,12 @@ int inet_frags_init(struct inet_frags *);
 void inet_frags_fini(struct inet_frags *);
 
 int fqdir_init(struct fqdir **fqdirp, struct inet_frags *f, struct net *net);
+
+static void inline fqdir_pre_exit(struct fqdir *fqdir)
+{
+	fqdir->high_thresh = 0; /* prevent creation of new frags */
+	fqdir->dead = true;
+}
 void fqdir_exit(struct fqdir *fqdir);
 
 void inet_frag_kill(struct inet_frag_queue *q);

include/net/ipv6_frag.h

@@ -67,6 +67,8 @@ ip6frag_expire_frag_queue(struct net *net, struct frag_queue *fq)
 	struct sk_buff *head;
 
 	rcu_read_lock();
+	if (fq->q.fqdir->dead)
+		goto out_rcu_unlock;
 	spin_lock(&fq->q.lock);
 
 	if (fq->q.flags & INET_FRAG_COMPLETE)

include/net/net_namespace.h

@@ -355,8 +355,13 @@ struct pernet_operations {
 	 * synchronize_rcu() related to these pernet_operations,
 	 * instead of separate synchronize_rcu() for every net.
 	 * Please, avoid synchronize_rcu() at all, where it's possible.
+	 *
+	 * Note that a combination of pre_exit() and exit() can
+	 * be used, since a synchronize_rcu() is guaranteed between
+	 * the calls.
 	 */
 	int (*init)(struct net *net);
+	void (*pre_exit)(struct net *net);
 	void (*exit)(struct net *net);
 	void (*exit_batch)(struct list_head *net_exit_list);
 	unsigned int *id;

net/core/net_namespace.c

@@ -145,6 +145,17 @@ static void ops_free(const struct pernet_operations *ops, struct net *net)
 	}
 }
 
+static void ops_pre_exit_list(const struct pernet_operations *ops,
+			      struct list_head *net_exit_list)
+{
+	struct net *net;
+
+	if (ops->pre_exit) {
+		list_for_each_entry(net, net_exit_list, exit_list)
+			ops->pre_exit(net);
+	}
+}
+
 static void ops_exit_list(const struct pernet_operations *ops,
 			  struct list_head *net_exit_list)
 {
@@ -328,6 +339,12 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
 	 * for the pernet modules whose init functions did not fail.
 	 */
 	list_add(&net->exit_list, &net_exit_list);
+	saved_ops = ops;
+	list_for_each_entry_continue_reverse(ops, &pernet_list, list)
+		ops_pre_exit_list(ops, &net_exit_list);
+
+	synchronize_rcu();
+
 	saved_ops = ops;
 	list_for_each_entry_continue_reverse(ops, &pernet_list, list)
 		ops_exit_list(ops, &net_exit_list);
@@ -541,10 +558,15 @@ static void cleanup_net(struct work_struct *work)
 		list_add_tail(&net->exit_list, &net_exit_list);
 	}
 
+	/* Run all of the network namespace pre_exit methods */
+	list_for_each_entry_reverse(ops, &pernet_list, list)
+		ops_pre_exit_list(ops, &net_exit_list);
+
 	/*
 	 * Another CPU might be rcu-iterating the list, wait for it.
 	 * This needs to be before calling the exit() notifiers, so
 	 * the rcu_barrier() below isn't sufficient alone.
+	 * Also the pre_exit() and exit() methods need this barrier.
 	 */
 	synchronize_rcu();
 
@@ -1101,6 +1123,8 @@ static int __register_pernet_operations(struct list_head *list,
 out_undo:
 	/* If I have an error cleanup all namespaces I initialized */
 	list_del(&ops->list);
+	ops_pre_exit_list(ops, &net_exit_list);
+	synchronize_rcu();
 	ops_exit_list(ops, &net_exit_list);
 	ops_free_list(ops, &net_exit_list);
 	return error;
@@ -1115,6 +1139,8 @@ static void __unregister_pernet_operations(struct pernet_operations *ops)
 	/* See comment in __register_pernet_operations() */
 	for_each_net(net)
 		list_add_tail(&net->exit_list, &net_exit_list);
+	ops_pre_exit_list(ops, &net_exit_list);
+	synchronize_rcu();
 	ops_exit_list(ops, &net_exit_list);
 	ops_free_list(ops, &net_exit_list);
 }
@@ -1139,6 +1165,8 @@ static void __unregister_pernet_operations(struct pernet_operations *ops)
 	} else {
 		LIST_HEAD(net_exit_list);
 		list_add(&init_net.exit_list, &net_exit_list);
+		ops_pre_exit_list(ops, &net_exit_list);
+		synchronize_rcu();
 		ops_exit_list(ops, &net_exit_list);
 		ops_free_list(ops, &net_exit_list);
 	}

net/ieee802154/6lowpan/reassembly.c

@@ -459,6 +459,14 @@ static int __net_init lowpan_frags_init_net(struct net *net)
 	return res;
 }
 
+static void __net_exit lowpan_frags_pre_exit_net(struct net *net)
+{
+	struct netns_ieee802154_lowpan *ieee802154_lowpan =
+		net_ieee802154_lowpan(net);
+
+	fqdir_pre_exit(ieee802154_lowpan->fqdir);
+}
+
 static void __net_exit lowpan_frags_exit_net(struct net *net)
 {
 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
@@ -469,8 +477,9 @@ static void __net_exit lowpan_frags_exit_net(struct net *net)
 }
 
 static struct pernet_operations lowpan_frags_ops = {
-	.init = lowpan_frags_init_net,
-	.exit = lowpan_frags_exit_net,
+	.init		= lowpan_frags_init_net,
+	.pre_exit	= lowpan_frags_pre_exit_net,
+	.exit		= lowpan_frags_exit_net,
 };
 
 static u32 lowpan_key_hashfn(const void *data, u32 len, u32 seed)

net/ipv4/inet_fragment.c

@@ -145,10 +145,9 @@ static void inet_frags_free_cb(void *ptr, void *arg)
 		inet_frag_destroy(fq);
 }
 
-static void fqdir_rwork_fn(struct work_struct *work)
+static void fqdir_work_fn(struct work_struct *work)
 {
-	struct fqdir *fqdir = container_of(to_rcu_work(work),
-					   struct fqdir, destroy_rwork);
+	struct fqdir *fqdir = container_of(work, struct fqdir, destroy_work);
 	struct inet_frags *f = fqdir->f;
 
 	rhashtable_free_and_destroy(&fqdir->rhashtable, inet_frags_free_cb, NULL);
@@ -187,18 +186,8 @@ EXPORT_SYMBOL(fqdir_init);
 
 void fqdir_exit(struct fqdir *fqdir)
 {
-	fqdir->high_thresh = 0; /* prevent creation of new frags */
-
-	fqdir->dead = true;
-
-	/* call_rcu is supposed to provide memory barrier semantics,
-	 * separating the setting of fqdir->dead with the destruction
-	 * work.  This implicit barrier is paired with inet_frag_kill().
-	 */
-
-	INIT_RCU_WORK(&fqdir->destroy_rwork, fqdir_rwork_fn);
-	queue_rcu_work(system_wq, &fqdir->destroy_rwork);
-
+	INIT_WORK(&fqdir->destroy_work, fqdir_work_fn);
+	queue_work(system_wq, &fqdir->destroy_work);
 }
 EXPORT_SYMBOL(fqdir_exit);
 

net/ipv4/ip_fragment.c

@@ -143,6 +143,10 @@ static void ip_expire(struct timer_list *t)
 	net = qp->q.fqdir->net;
 
 	rcu_read_lock();
+
+	if (qp->q.fqdir->dead)
+		goto out_rcu_unlock;
+
 	spin_lock(&qp->q.lock);
 
 	if (qp->q.flags & INET_FRAG_COMPLETE)
@@ -676,6 +680,11 @@ static int __net_init ipv4_frags_init_net(struct net *net)
 	return res;
 }
 
+static void __net_exit ipv4_frags_pre_exit_net(struct net *net)
+{
+	fqdir_pre_exit(net->ipv4.fqdir);
+}
+
 static void __net_exit ipv4_frags_exit_net(struct net *net)
 {
 	ip4_frags_ns_ctl_unregister(net);
@@ -683,8 +692,9 @@ static void __net_exit ipv4_frags_exit_net(struct net *net)
 }
 
 static struct pernet_operations ip4_frags_ops = {
-	.init = ipv4_frags_init_net,
-	.exit = ipv4_frags_exit_net,
+	.init		= ipv4_frags_init_net,
+	.pre_exit	= ipv4_frags_pre_exit_net,
+	.exit		= ipv4_frags_exit_net,
 };
 
 

net/ipv6/netfilter/nf_conntrack_reasm.c

@@ -499,6 +499,11 @@ static int nf_ct_net_init(struct net *net)
 	return res;
 }
 
+static void nf_ct_net_pre_exit(struct net *net)
+{
+	fqdir_pre_exit(net->nf_frag.fqdir);
+}
+
 static void nf_ct_net_exit(struct net *net)
 {
 	nf_ct_frags6_sysctl_unregister(net);
@@ -506,8 +511,9 @@ static void nf_ct_net_exit(struct net *net)
 }
 
 static struct pernet_operations nf_ct_net_ops = {
-	.init = nf_ct_net_init,
-	.exit = nf_ct_net_exit,
+	.init		= nf_ct_net_init,
+	.pre_exit	= nf_ct_net_pre_exit,
+	.exit		= nf_ct_net_exit,
 };
 
 static const struct rhashtable_params nfct_rhash_params = {

net/ipv6/reassembly.c

@@ -520,6 +520,11 @@ static int __net_init ipv6_frags_init_net(struct net *net)
 	return res;
 }
 
+static void __net_exit ipv6_frags_pre_exit_net(struct net *net)
+{
+	fqdir_pre_exit(net->ipv6.fqdir);
+}
+
 static void __net_exit ipv6_frags_exit_net(struct net *net)
 {
 	ip6_frags_ns_sysctl_unregister(net);
@@ -527,8 +532,9 @@ static void __net_exit ipv6_frags_exit_net(struct net *net)
 }
 
 static struct pernet_operations ip6_frags_ops = {
-	.init = ipv6_frags_init_net,
-	.exit = ipv6_frags_exit_net,
+	.init		= ipv6_frags_init_net,
+	.pre_exit	= ipv6_frags_pre_exit_net,
+	.exit		= ipv6_frags_exit_net,
 };
 
 static const struct rhashtable_params ip6_rhash_params = {