Message-ID: <152240169991.24910.6978707493362813761.stgit@localhost.localdomain>
Date:   Fri, 30 Mar 2018 12:23:21 +0300
From:   Kirill Tkhai <ktkhai@...tuozzo.com>
To:     davem@...emloft.net, ktkhai@...tuozzo.com, netdev@...r.kernel.org
Subject: [PATCH net-next] net: Revert net_rwsem

This reverts:

152f253152cc net: Remove rtnl_lock() in nf_ct_iterate_destroy()
ec9c780925c5 ovs: Remove rtnl_lock() from ovs_exit_net()
350311aab4c0 security: Remove rtnl_lock() in selinux_xfrm_notify_policyload()
10256debb918 net: Don't take rtnl_lock() in wireless_nlevent_flush()
f0b07bb151b0 net: Introduce net_rwsem to protect net_namespace_list

There are missed, that down_read() can't be taken recursive.
This is because of rw_semaphore design, which prevents it
to be occupied by only readers forever.

So, we can't take it in register_netdevice_notifier(), as it's also
taken in wext_netdev_notifier_call()->wireless_nlevent_flush().

The solution is to protect net_namespace_list modifications
in register_netdevice_notifier() via pernet_ops_rwsem, as it's
made in:

https://patchwork.ozlabs.org/project/netdev/list/?series=36495

Then, we won't have to take net_rwsem in call_netevent_notifiers().

But since the patchset is not in kernel, let's just revert net_rwsem
for now, and I'll resubmit it later (after the above patchset).

Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>
---
 drivers/infiniband/core/roce_gid_mgmt.c |    2 --
 include/linux/rtnetlink.h               |    1 -
 include/net/net_namespace.h             |    1 -
 net/core/dev.c                          |    5 -----
 net/core/fib_notifier.c                 |    2 --
 net/core/net_namespace.c                |   18 +++++-------------
 net/core/rtnetlink.c                    |    5 -----
 net/netfilter/nf_conntrack_core.c       |    4 ++--
 net/openvswitch/datapath.c              |    4 ++--
 net/wireless/wext-core.c                |    6 ++++--
 security/selinux/include/xfrm.h         |    4 ++--
 11 files changed, 15 insertions(+), 37 deletions(-)

diff --git a/drivers/infiniband/core/roce_gid_mgmt.c b/drivers/infiniband/core/roce_gid_mgmt.c
index cc2966380c0c..5a52ec77940a 100644
--- a/drivers/infiniband/core/roce_gid_mgmt.c
+++ b/drivers/infiniband/core/roce_gid_mgmt.c
@@ -403,12 +403,10 @@ static void enum_all_gids_of_dev_cb(struct ib_device *ib_dev,
 	 * our feet
 	 */
 	rtnl_lock();
-	down_read(&net_rwsem);
 	for_each_net(net)
 		for_each_netdev(net, ndev)
 			if (is_eth_port_of_netdev(ib_dev, port, rdma_ndev, ndev))
 				add_netdev_ips(ib_dev, port, rdma_ndev, ndev);
-	up_read(&net_rwsem);
 	rtnl_unlock();
 }
 
diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 5225832bd6ff..c7d1e4689325 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -37,7 +37,6 @@ extern int rtnl_lock_killable(void);
 
 extern wait_queue_head_t netdev_unregistering_wq;
 extern struct rw_semaphore pernet_ops_rwsem;
-extern struct rw_semaphore net_rwsem;
 
 #ifdef CONFIG_PROVE_LOCKING
 extern bool lockdep_rtnl_is_held(void);
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 47e35cce3b64..1ab4f920f109 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -291,7 +291,6 @@ static inline struct net *read_pnet(const possible_net_t *pnet)
 #endif
 }
 
-/* Protected by net_rwsem */
 #define for_each_net(VAR)				\
 	list_for_each_entry(VAR, &net_namespace_list, list)
 
diff --git a/net/core/dev.c b/net/core/dev.c
index eca5458b2753..e13807b5c84d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1629,7 +1629,6 @@ int register_netdevice_notifier(struct notifier_block *nb)
 		goto unlock;
 	if (dev_boot_phase)
 		goto unlock;
-	down_read(&net_rwsem);
 	for_each_net(net) {
 		for_each_netdev(net, dev) {
 			err = call_netdevice_notifier(nb, NETDEV_REGISTER, dev);
@@ -1643,7 +1642,6 @@ int register_netdevice_notifier(struct notifier_block *nb)
 			call_netdevice_notifier(nb, NETDEV_UP, dev);
 		}
 	}
-	up_read(&net_rwsem);
 
 unlock:
 	rtnl_unlock();
@@ -1666,7 +1664,6 @@ int register_netdevice_notifier(struct notifier_block *nb)
 	}
 
 outroll:
-	up_read(&net_rwsem);
 	raw_notifier_chain_unregister(&netdev_chain, nb);
 	goto unlock;
 }
@@ -1697,7 +1694,6 @@ int unregister_netdevice_notifier(struct notifier_block *nb)
 	if (err)
 		goto unlock;
 
-	down_read(&net_rwsem);
 	for_each_net(net) {
 		for_each_netdev(net, dev) {
 			if (dev->flags & IFF_UP) {
@@ -1708,7 +1704,6 @@ int unregister_netdevice_notifier(struct notifier_block *nb)
 			call_netdevice_notifier(nb, NETDEV_UNREGISTER, dev);
 		}
 	}
-	up_read(&net_rwsem);
 unlock:
 	rtnl_unlock();
 	return err;
diff --git a/net/core/fib_notifier.c b/net/core/fib_notifier.c
index 13a40b831d6d..b793b523aba3 100644
--- a/net/core/fib_notifier.c
+++ b/net/core/fib_notifier.c
@@ -39,7 +39,6 @@ static unsigned int fib_seq_sum(void)
 	struct net *net;
 
 	rtnl_lock();
-	down_read(&net_rwsem);
 	for_each_net(net) {
 		rcu_read_lock();
 		list_for_each_entry_rcu(ops, &net->fib_notifier_ops, list) {
@@ -50,7 +49,6 @@ static unsigned int fib_seq_sum(void)
 		}
 		rcu_read_unlock();
 	}
-	up_read(&net_rwsem);
 	rtnl_unlock();
 
 	return fib_seq;
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 7fdf321d4997..b5796d17a302 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -33,10 +33,6 @@ static struct list_head *first_device = &pernet_list;
 LIST_HEAD(net_namespace_list);
 EXPORT_SYMBOL_GPL(net_namespace_list);
 
-/* Protects net_namespace_list. Nests iside rtnl_lock() */
-DECLARE_RWSEM(net_rwsem);
-EXPORT_SYMBOL_GPL(net_rwsem);
-
 struct net init_net = {
 	.count		= REFCOUNT_INIT(1),
 	.dev_base_head	= LIST_HEAD_INIT(init_net.dev_base_head),
@@ -313,9 +309,9 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
 		if (error < 0)
 			goto out_undo;
 	}
-	down_write(&net_rwsem);
+	rtnl_lock();
 	list_add_tail_rcu(&net->list, &net_namespace_list);
-	up_write(&net_rwsem);
+	rtnl_unlock();
 out:
 	return error;
 
@@ -454,7 +450,7 @@ static void unhash_nsid(struct net *net, struct net *last)
 	 * and this work is the only process, that may delete
 	 * a net from net_namespace_list. So, when the below
 	 * is executing, the list may only grow. Thus, we do not
-	 * use for_each_net_rcu() or net_rwsem.
+	 * use for_each_net_rcu() or rtnl_lock().
 	 */
 	for_each_net(tmp) {
 		int id;
@@ -489,7 +485,7 @@ static void cleanup_net(struct work_struct *work)
 	down_read(&pernet_ops_rwsem);
 
 	/* Don't let anyone else find us. */
-	down_write(&net_rwsem);
+	rtnl_lock();
 	llist_for_each_entry(net, net_kill_list, cleanup_list)
 		list_del_rcu(&net->list);
 	/* Cache last net. After we unlock rtnl, no one new net
@@ -503,7 +499,7 @@ static void cleanup_net(struct work_struct *work)
 	 * useless anyway, as netns_ids are destroyed there.
 	 */
 	last = list_last_entry(&net_namespace_list, struct net, list);
-	up_write(&net_rwsem);
+	rtnl_unlock();
 
 	llist_for_each_entry(net, net_kill_list, cleanup_list) {
 		unhash_nsid(net, last);
@@ -904,9 +900,6 @@ static int __register_pernet_operations(struct list_head *list,
 
 	list_add_tail(&ops->list, list);
 	if (ops->init || (ops->id && ops->size)) {
-		/* We held write locked pernet_ops_rwsem, and parallel
-		 * setup_net() and cleanup_net() are not possible.
-		 */
 		for_each_net(net) {
 			error = ops_init(ops, net);
 			if (error)
@@ -930,7 +923,6 @@ static void __unregister_pernet_operations(struct pernet_operations *ops)
 	LIST_HEAD(net_exit_list);
 
 	list_del(&ops->list);
-	/* See comment in __register_pernet_operations() */
 	for_each_net(net)
 		list_add_tail(&net->exit_list, &net_exit_list);
 	ops_exit_list(ops, &net_exit_list);
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index e86b28482ca7..2d3949789cef 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -418,11 +418,9 @@ void __rtnl_link_unregister(struct rtnl_link_ops *ops)
 {
 	struct net *net;
 
-	down_read(&net_rwsem);
 	for_each_net(net) {
 		__rtnl_kill_links(net, ops);
 	}
-	up_read(&net_rwsem);
 	list_del(&ops->list);
 }
 EXPORT_SYMBOL_GPL(__rtnl_link_unregister);
@@ -440,9 +438,6 @@ static void rtnl_lock_unregistering_all(void)
 	for (;;) {
 		unregistering = false;
 		rtnl_lock();
-		/* We held write locked pernet_ops_rwsem, and parallel
-		 * setup_net() and cleanup_net() are not possible.
-		 */
 		for_each_net(net) {
 			if (net->dev_unreg_count > 0) {
 				unregistering = true;
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 41ff04ee2554..705198de671d 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1763,14 +1763,14 @@ nf_ct_iterate_destroy(int (*iter)(struct nf_conn *i, void *data), void *data)
 {
 	struct net *net;
 
-	down_read(&net_rwsem);
+	rtnl_lock();
 	for_each_net(net) {
 		if (atomic_read(&net->ct.count) == 0)
 			continue;
 		__nf_ct_unconfirmed_destroy(net);
 		nf_queue_nf_hook_drop(net);
 	}
-	up_read(&net_rwsem);
+	rtnl_unlock();
 
 	/* Need to wait for netns cleanup worker to finish, if its
 	 * running -- it might have deleted a net namespace from
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 015e24e08909..ef38e5aecd28 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -2363,10 +2363,10 @@ static void __net_exit ovs_exit_net(struct net *dnet)
 	list_for_each_entry_safe(dp, dp_next, &ovs_net->dps, list_node)
 		__dp_destroy(dp);
 
-	down_read(&net_rwsem);
+	rtnl_lock();
 	for_each_net(net)
 		list_vports_from_net(net, dnet, &head);
-	up_read(&net_rwsem);
+	rtnl_unlock();
 
 	/* Detach all vports from given namespace. */
 	list_for_each_entry_safe(vport, vport_next, &head, detach_list) {
diff --git a/net/wireless/wext-core.c b/net/wireless/wext-core.c
index 5e677dac2a0c..9efbfc753347 100644
--- a/net/wireless/wext-core.c
+++ b/net/wireless/wext-core.c
@@ -347,13 +347,13 @@ void wireless_nlevent_flush(void)
 	struct sk_buff *skb;
 	struct net *net;
 
-	down_read(&net_rwsem);
+	ASSERT_RTNL();
+
 	for_each_net(net) {
 		while ((skb = skb_dequeue(&net->wext_nlevents)))
 			rtnl_notify(skb, net, 0, RTNLGRP_LINK, NULL,
 				    GFP_KERNEL);
 	}
-	up_read(&net_rwsem);
 }
 EXPORT_SYMBOL_GPL(wireless_nlevent_flush);
 
@@ -410,7 +410,9 @@ subsys_initcall(wireless_nlevent_init);
 /* Process events generated by the wireless layer or the driver. */
 static void wireless_nlevent_process(struct work_struct *work)
 {
+	rtnl_lock();
 	wireless_nlevent_flush();
+	rtnl_unlock();
 }
 
 static DECLARE_WORK(wireless_nlevent_work, wireless_nlevent_process);
diff --git a/security/selinux/include/xfrm.h b/security/selinux/include/xfrm.h
index a0b465316292..1f173a7a4daa 100644
--- a/security/selinux/include/xfrm.h
+++ b/security/selinux/include/xfrm.h
@@ -47,10 +47,10 @@ static inline void selinux_xfrm_notify_policyload(void)
 {
 	struct net *net;
 
-	down_read(&net_rwsem);
+	rtnl_lock();
 	for_each_net(net)
 		rt_genid_bump_all(net);
-	up_read(&net_rwsem);
+	rtnl_unlock();
 }
 #else
 static inline int selinux_xfrm_enabled(void)

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