[PATCH 25/37] netfilter: ipt_CLUSTERIP: fix deadlock in netns exit routine

[Pablo Neira Ayuso <pablo@netfilter.org>]

From: Taehee Yoo <ap420073@gmail.com>

When network namespace is destroyed, cleanup_net() is called.
cleanup_net() holds pernet_ops_rwsem then calls each ->exit callback.
So that clusterip_tg_destroy() is called by cleanup_net().
And clusterip_tg_destroy() calls unregister_netdevice_notifier().

But both cleanup_net() and clusterip_tg_destroy() hold same
lock(pernet_ops_rwsem). hence deadlock occurrs.

After this patch, only 1 notifier is registered when module is inserted.
And all of configs are added to per-net list.

test commands:
   %ip netns add vm1
   %ip netns exec vm1 bash
   %ip link set lo up
   %iptables -A INPUT -p tcp -i lo -d 192.168.0.5 --dport 80 \
	-j CLUSTERIP --new --hashmode sourceip \
	--clustermac 01:00:5e:00:00:20 --total-nodes 2 --local-node 1
   %exit
   %ip netns del vm1

splat looks like:
[  341.809674] ============================================
[  341.809674] WARNING: possible recursive locking detected
[  341.809674] 4.19.0-rc5+ #16 Tainted: G        W
[  341.809674] --------------------------------------------
[  341.809674] kworker/u4:2/87 is trying to acquire lock:
[  341.809674] 000000005da2d519 (pernet_ops_rwsem){++++}, at: unregister_netdevice_notifier+0x8c/0x460
[  341.809674]
[  341.809674] but task is already holding lock:
[  341.809674] 000000005da2d519 (pernet_ops_rwsem){++++}, at: cleanup_net+0x119/0x900
[  341.809674]
[  341.809674] other info that might help us debug this:
[  341.809674]  Possible unsafe locking scenario:
[  341.809674]
[  341.809674]        CPU0
[  341.809674]        ----
[  341.809674]   lock(pernet_ops_rwsem);
[  341.809674]   lock(pernet_ops_rwsem);
[  341.809674]
[  341.809674]  *** DEADLOCK ***
[  341.809674]
[  341.809674]  May be due to missing lock nesting notation
[  341.809674]
[  341.809674] 3 locks held by kworker/u4:2/87:
[  341.809674]  #0: 00000000d9df6c92 ((wq_completion)"%s""netns"){+.+.}, at: process_one_work+0xafe/0x1de0
[  341.809674]  #1: 00000000c2cbcee2 (net_cleanup_work){+.+.}, at: process_one_work+0xb60/0x1de0
[  341.809674]  #2: 000000005da2d519 (pernet_ops_rwsem){++++}, at: cleanup_net+0x119/0x900
[  341.809674]
[  341.809674] stack backtrace:
[  341.809674] CPU: 1 PID: 87 Comm: kworker/u4:2 Tainted: G        W         4.19.0-rc5+ #16
[  341.809674] Workqueue: netns cleanup_net
[  341.809674] Call Trace:
[ ... ]
[  342.070196]  down_write+0x93/0x160
[  342.070196]  ? unregister_netdevice_notifier+0x8c/0x460
[  342.070196]  ? down_read+0x1e0/0x1e0
[  342.070196]  ? sched_clock_cpu+0x126/0x170
[  342.070196]  ? find_held_lock+0x39/0x1c0
[  342.070196]  unregister_netdevice_notifier+0x8c/0x460
[  342.070196]  ? register_netdevice_notifier+0x790/0x790
[  342.070196]  ? __local_bh_enable_ip+0xe9/0x1b0
[  342.070196]  ? __local_bh_enable_ip+0xe9/0x1b0
[  342.070196]  ? clusterip_tg_destroy+0x372/0x650 [ipt_CLUSTERIP]
[  342.070196]  ? trace_hardirqs_on+0x93/0x210
[  342.070196]  ? __bpf_trace_preemptirq_template+0x10/0x10
[  342.070196]  ? clusterip_tg_destroy+0x372/0x650 [ipt_CLUSTERIP]
[  342.123094]  clusterip_tg_destroy+0x3ad/0x650 [ipt_CLUSTERIP]
[  342.123094]  ? clusterip_net_init+0x3d0/0x3d0 [ipt_CLUSTERIP]
[  342.123094]  ? cleanup_match+0x17d/0x200 [ip_tables]
[  342.123094]  ? xt_unregister_table+0x215/0x300 [x_tables]
[  342.123094]  ? kfree+0xe2/0x2a0
[  342.123094]  cleanup_entry+0x1d5/0x2f0 [ip_tables]
[  342.123094]  ? cleanup_match+0x200/0x200 [ip_tables]
[  342.123094]  __ipt_unregister_table+0x9b/0x1a0 [ip_tables]
[  342.123094]  iptable_filter_net_exit+0x43/0x80 [iptable_filter]
[  342.123094]  ops_exit_list.isra.10+0x94/0x140
[  342.123094]  cleanup_net+0x45b/0x900
[ ... ]

Fixes: 202f59afd441 ("netfilter: ipt_CLUSTERIP: do not hold dev")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/ipv4/netfilter/ipt_CLUSTERIP.c | 155 +++++++++++++++++++++----------------
 1 file changed, 87 insertions(+), 68 deletions(-)

diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c
index 5b0c1ee6ae26..091d163d215b 100644
--- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -57,17 +57,14 @@ struct clusterip_config {
 	enum clusterip_hashmode hash_mode;	/* which hashing mode */
 	u_int32_t hash_initval;			/* hash initialization */
 	struct rcu_head rcu;
-
+	struct net *net;			/* netns for pernet list */
 	char ifname[IFNAMSIZ];			/* device ifname */
-	struct notifier_block notifier;		/* refresh c->ifindex in it */
 };
 
 #ifdef CONFIG_PROC_FS
 static const struct file_operations clusterip_proc_fops;
 #endif
 
-static unsigned int clusterip_net_id __read_mostly;
-
 struct clusterip_net {
 	struct list_head configs;
 	/* lock protects the configs list */
@@ -78,16 +75,30 @@ struct clusterip_net {
 #endif
 };
 
+static unsigned int clusterip_net_id __read_mostly;
+static inline struct clusterip_net *clusterip_pernet(struct net *net)
+{
+	return net_generic(net, clusterip_net_id);
+}
+
 static inline void
 clusterip_config_get(struct clusterip_config *c)
 {
 	refcount_inc(&c->refcount);
 }
 
-
 static void clusterip_config_rcu_free(struct rcu_head *head)
 {
-	kfree(container_of(head, struct clusterip_config, rcu));
+	struct clusterip_config *config;
+	struct net_device *dev;
+
+	config = container_of(head, struct clusterip_config, rcu);
+	dev = dev_get_by_name(config->net, config->ifname);
+	if (dev) {
+		dev_mc_del(dev, config->clustermac);
+		dev_put(dev);
+	}
+	kfree(config);
 }
 
 static inline void
@@ -101,9 +112,9 @@ clusterip_config_put(struct clusterip_config *c)
  * entry(rule) is removed, remove the config from lists, but don't free it
  * yet, since proc-files could still be holding references */
 static inline void
-clusterip_config_entry_put(struct net *net, struct clusterip_config *c)
+clusterip_config_entry_put(struct clusterip_config *c)
 {
-	struct clusterip_net *cn = net_generic(net, clusterip_net_id);
+	struct clusterip_net *cn = clusterip_pernet(c->net);
 
 	local_bh_disable();
 	if (refcount_dec_and_lock(&c->entries, &cn->lock)) {
@@ -118,8 +129,6 @@ clusterip_config_entry_put(struct net *net, struct clusterip_config *c)
 		spin_unlock(&cn->lock);
 		local_bh_enable();
 
-		unregister_netdevice_notifier(&c->notifier);
-
 		return;
 	}
 	local_bh_enable();
@@ -129,7 +138,7 @@ static struct clusterip_config *
 __clusterip_config_find(struct net *net, __be32 clusterip)
 {
 	struct clusterip_config *c;
-	struct clusterip_net *cn = net_generic(net, clusterip_net_id);
+	struct clusterip_net *cn = clusterip_pernet(net);
 
 	list_for_each_entry_rcu(c, &cn->configs, list) {
 		if (c->clusterip == clusterip)
@@ -181,32 +190,37 @@ clusterip_netdev_event(struct notifier_block *this, unsigned long event,
 		       void *ptr)
 {
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct net *net = dev_net(dev);
+	struct clusterip_net *cn = clusterip_pernet(net);
 	struct clusterip_config *c;
 
-	c = container_of(this, struct clusterip_config, notifier);
-	switch (event) {
-	case NETDEV_REGISTER:
-		if (!strcmp(dev->name, c->ifname)) {
-			c->ifindex = dev->ifindex;
-			dev_mc_add(dev, c->clustermac);
-		}
-		break;
-	case NETDEV_UNREGISTER:
-		if (dev->ifindex == c->ifindex) {
-			dev_mc_del(dev, c->clustermac);
-			c->ifindex = -1;
-		}
-		break;
-	case NETDEV_CHANGENAME:
-		if (!strcmp(dev->name, c->ifname)) {
-			c->ifindex = dev->ifindex;
-			dev_mc_add(dev, c->clustermac);
-		} else if (dev->ifindex == c->ifindex) {
-			dev_mc_del(dev, c->clustermac);
-			c->ifindex = -1;
+	spin_lock_bh(&cn->lock);
+	list_for_each_entry_rcu(c, &cn->configs, list) {
+		switch (event) {
+		case NETDEV_REGISTER:
+			if (!strcmp(dev->name, c->ifname)) {
+				c->ifindex = dev->ifindex;
+				dev_mc_add(dev, c->clustermac);
+			}
+			break;
+		case NETDEV_UNREGISTER:
+			if (dev->ifindex == c->ifindex) {
+				dev_mc_del(dev, c->clustermac);
+				c->ifindex = -1;
+			}
+			break;
+		case NETDEV_CHANGENAME:
+			if (!strcmp(dev->name, c->ifname)) {
+				c->ifindex = dev->ifindex;
+				dev_mc_add(dev, c->clustermac);
+			} else if (dev->ifindex == c->ifindex) {
+				dev_mc_del(dev, c->clustermac);
+				c->ifindex = -1;
+			}
+			break;
 		}
-		break;
 	}
+	spin_unlock_bh(&cn->lock);
 
 	return NOTIFY_DONE;
 }
@@ -215,30 +229,44 @@ static struct clusterip_config *
 clusterip_config_init(struct net *net, const struct ipt_clusterip_tgt_info *i,
 		      __be32 ip, const char *iniface)
 {
-	struct clusterip_net *cn = net_generic(net, clusterip_net_id);
+	struct clusterip_net *cn = clusterip_pernet(net);
 	struct clusterip_config *c;
+	struct net_device *dev;
 	int err;
 
+	if (iniface[0] == '\0') {
+		pr_info("Please specify an interface name\n");
+		return ERR_PTR(-EINVAL);
+	}
+
 	c = kzalloc(sizeof(*c), GFP_ATOMIC);
 	if (!c)
 		return ERR_PTR(-ENOMEM);
 
-	strcpy(c->ifname, iniface);
-	c->ifindex = -1;
-	c->clusterip = ip;
+	dev = dev_get_by_name(net, iniface);
+	if (!dev) {
+		pr_info("no such interface %s\n", iniface);
+		kfree(c);
+		return ERR_PTR(-ENOENT);
+	}
+	c->ifindex = dev->ifindex;
+	strcpy(c->ifname, dev->name);
 	memcpy(&c->clustermac, &i->clustermac, ETH_ALEN);
+	dev_mc_add(dev, c->clustermac);
+	dev_put(dev);
+
+	c->clusterip = ip;
 	c->num_total_nodes = i->num_total_nodes;
 	clusterip_config_init_nodelist(c, i);
 	c->hash_mode = i->hash_mode;
 	c->hash_initval = i->hash_initval;
+	c->net = net;
 	refcount_set(&c->refcount, 1);
 
 	spin_lock_bh(&cn->lock);
 	if (__clusterip_config_find(net, ip)) {
-		spin_unlock_bh(&cn->lock);
-		kfree(c);
-
-		return ERR_PTR(-EBUSY);
+		err = -EBUSY;
+		goto out_config_put;
 	}
 
 	list_add_rcu(&c->list, &cn->configs);
@@ -260,22 +288,17 @@ clusterip_config_init(struct net *net, const struct ipt_clusterip_tgt_info *i,
 	}
 #endif
 
-	c->notifier.notifier_call = clusterip_netdev_event;
-	err = register_netdevice_notifier(&c->notifier);
-	if (!err) {
-		refcount_set(&c->entries, 1);
-		return c;
-	}
+	refcount_set(&c->entries, 1);
+	return c;
 
 #ifdef CONFIG_PROC_FS
-	proc_remove(c->pde);
 err:
 #endif
 	spin_lock_bh(&cn->lock);
 	list_del_rcu(&c->list);
+out_config_put:
 	spin_unlock_bh(&cn->lock);
 	clusterip_config_put(c);
-
 	return ERR_PTR(err);
 }
 
@@ -475,21 +498,6 @@ static int clusterip_tg_check(const struct xt_tgchk_param *par)
 				&e->ip.dst.s_addr);
 			return -EINVAL;
 		} else {
-			struct net_device *dev;
-
-			if (e->ip.iniface[0] == '\0') {
-				pr_info("Please specify an interface name\n");
-				return -EINVAL;
-			}
-
-			dev = dev_get_by_name(par->net, e->ip.iniface);
-			if (!dev) {
-				pr_info("no such interface %s\n",
-					e->ip.iniface);
-				return -ENOENT;
-			}
-			dev_put(dev);
-
 			config = clusterip_config_init(par->net, cipinfo,
 						       e->ip.dst.s_addr,
 						       e->ip.iniface);
@@ -502,7 +510,7 @@ static int clusterip_tg_check(const struct xt_tgchk_param *par)
 	if (ret < 0) {
 		pr_info("cannot load conntrack support for proto=%u\n",
 			par->family);
-		clusterip_config_entry_put(par->net, config);
+		clusterip_config_entry_put(config);
 		clusterip_config_put(config);
 		return ret;
 	}
@@ -524,7 +532,7 @@ static void clusterip_tg_destroy(const struct xt_tgdtor_param *par)
 
 	/* if no more entries are referencing the config, remove it
 	 * from the list and destroy the proc entry */
-	clusterip_config_entry_put(par->net, cipinfo->config);
+	clusterip_config_entry_put(cipinfo->config);
 
 	clusterip_config_put(cipinfo->config);
 
@@ -806,7 +814,7 @@ static const struct file_operations clusterip_proc_fops = {
 
 static int clusterip_net_init(struct net *net)
 {
-	struct clusterip_net *cn = net_generic(net, clusterip_net_id);
+	struct clusterip_net *cn = clusterip_pernet(net);
 	int ret;
 
 	INIT_LIST_HEAD(&cn->configs);
@@ -831,7 +839,7 @@ static int clusterip_net_init(struct net *net)
 
 static void clusterip_net_exit(struct net *net)
 {
-	struct clusterip_net *cn = net_generic(net, clusterip_net_id);
+	struct clusterip_net *cn = clusterip_pernet(net);
 #ifdef CONFIG_PROC_FS
 	proc_remove(cn->procdir);
 	cn->procdir = NULL;
@@ -847,6 +855,10 @@ static struct pernet_operations clusterip_net_ops = {
 	.size = sizeof(struct clusterip_net),
 };
 
+struct notifier_block cip_netdev_notifier = {
+	.notifier_call = clusterip_netdev_event
+};
+
 static int __init clusterip_tg_init(void)
 {
 	int ret;
@@ -859,11 +871,17 @@ static int __init clusterip_tg_init(void)
 	if (ret < 0)
 		goto cleanup_subsys;
 
+	ret = register_netdevice_notifier(&cip_netdev_notifier);
+	if (ret < 0)
+		goto unregister_target;
+
 	pr_info("ClusterIP Version %s loaded successfully\n",
 		CLUSTERIP_VERSION);
 
 	return 0;
 
+unregister_target:
+	xt_unregister_target(&clusterip_tg_reg);
 cleanup_subsys:
 	unregister_pernet_subsys(&clusterip_net_ops);
 	return ret;
@@ -873,6 +891,7 @@ static void __exit clusterip_tg_exit(void)
 {
 	pr_info("ClusterIP Version %s unloading\n", CLUSTERIP_VERSION);
 
+	unregister_netdevice_notifier(&cip_netdev_notifier);
 	xt_unregister_target(&clusterip_tg_reg);
 	unregister_pernet_subsys(&clusterip_net_ops);
 
-- 
2.11.0