[02/12] ipvs: fix rtnl_lock lockups caused by start_sync_thread

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 5ebde4b15810..f36098887ad0 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -2384,11 +2384,7 @@  do_ip_vs_set_ctl(struct sock *sk, int cmd, void __user *user, unsigned int len)
 			strlcpy(cfg.mcast_ifn, dm->mcast_ifn,
 				sizeof(cfg.mcast_ifn));
 			cfg.syncid = dm->syncid;
-			rtnl_lock();
-			mutex_lock(&ipvs->sync_mutex);
 			ret = start_sync_thread(ipvs, &cfg, dm->state);
-			mutex_unlock(&ipvs->sync_mutex);
-			rtnl_unlock();
 		} else {
 			mutex_lock(&ipvs->sync_mutex);
 			ret = stop_sync_thread(ipvs, dm->state);
@@ -3481,12 +3477,8 @@  static int ip_vs_genl_new_daemon(struct netns_ipvs *ipvs, struct nlattr **attrs)
 	if (ipvs->mixed_address_family_dests > 0)
 		return -EINVAL;
 
-	rtnl_lock();
-	mutex_lock(&ipvs->sync_mutex);
 	ret = start_sync_thread(ipvs, &c,
 				nla_get_u32(attrs[IPVS_DAEMON_ATTR_STATE]));
-	mutex_unlock(&ipvs->sync_mutex);
-	rtnl_unlock();
 	return ret;
 }
 
diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c
index fbaf3bd05b2e..001501e25625 100644
--- a/net/netfilter/ipvs/ip_vs_sync.c
+++ b/net/netfilter/ipvs/ip_vs_sync.c
@@ -49,6 +49,7 @@ 
 #include <linux/kthread.h>
 #include <linux/wait.h>
 #include <linux/kernel.h>
+#include <linux/sched/signal.h>
 
 #include <asm/unaligned.h>		/* Used for ntoh_seq and hton_seq */
 
@@ -1360,15 +1361,9 @@  static void set_mcast_pmtudisc(struct sock *sk, int val)
 /*
  *      Specifiy default interface for outgoing multicasts
  */
-static int set_mcast_if(struct sock *sk, char *ifname)
+static int set_mcast_if(struct sock *sk, struct net_device *dev)
 {
-	struct net_device *dev;
 	struct inet_sock *inet = inet_sk(sk);
-	struct net *net = sock_net(sk);
-
-	dev = __dev_get_by_name(net, ifname);
-	if (!dev)
-		return -ENODEV;
 
 	if (sk->sk_bound_dev_if && dev->ifindex != sk->sk_bound_dev_if)
 		return -EINVAL;
@@ -1396,19 +1391,14 @@  static int set_mcast_if(struct sock *sk, char *ifname)
  *      in the in_addr structure passed in as a parameter.
  */
 static int
-join_mcast_group(struct sock *sk, struct in_addr *addr, char *ifname)
+join_mcast_group(struct sock *sk, struct in_addr *addr, struct net_device *dev)
 {
-	struct net *net = sock_net(sk);
 	struct ip_mreqn mreq;
-	struct net_device *dev;
 	int ret;
 
 	memset(&mreq, 0, sizeof(mreq));
 	memcpy(&mreq.imr_multiaddr, addr, sizeof(struct in_addr));
 
-	dev = __dev_get_by_name(net, ifname);
-	if (!dev)
-		return -ENODEV;
 	if (sk->sk_bound_dev_if && dev->ifindex != sk->sk_bound_dev_if)
 		return -EINVAL;
 
@@ -1423,15 +1413,10 @@  join_mcast_group(struct sock *sk, struct in_addr *addr, char *ifname)
 
 #ifdef CONFIG_IP_VS_IPV6
 static int join_mcast_group6(struct sock *sk, struct in6_addr *addr,
-			     char *ifname)
+			     struct net_device *dev)
 {
-	struct net *net = sock_net(sk);
-	struct net_device *dev;
 	int ret;
 
-	dev = __dev_get_by_name(net, ifname);
-	if (!dev)
-		return -ENODEV;
 	if (sk->sk_bound_dev_if && dev->ifindex != sk->sk_bound_dev_if)
 		return -EINVAL;
 
@@ -1443,24 +1428,18 @@  static int join_mcast_group6(struct sock *sk, struct in6_addr *addr,
 }
 #endif
 
-static int bind_mcastif_addr(struct socket *sock, char *ifname)
+static int bind_mcastif_addr(struct socket *sock, struct net_device *dev)
 {
-	struct net *net = sock_net(sock->sk);
-	struct net_device *dev;
 	__be32 addr;
 	struct sockaddr_in sin;
 
-	dev = __dev_get_by_name(net, ifname);
-	if (!dev)
-		return -ENODEV;
-
 	addr = inet_select_addr(dev, 0, RT_SCOPE_UNIVERSE);
 	if (!addr)
 		pr_err("You probably need to specify IP address on "
 		       "multicast interface.\n");
 
 	IP_VS_DBG(7, "binding socket with (%s) %pI4\n",
-		  ifname, &addr);
+		  dev->name, &addr);
 
 	/* Now bind the socket with the address of multicast interface */
 	sin.sin_family	     = AF_INET;
@@ -1493,7 +1472,8 @@  static void get_mcast_sockaddr(union ipvs_sockaddr *sa, int *salen,
 /*
  *      Set up sending multicast socket over UDP
  */
-static struct socket *make_send_sock(struct netns_ipvs *ipvs, int id)
+static int make_send_sock(struct netns_ipvs *ipvs, int id,
+			  struct net_device *dev, struct socket **sock_ret)
 {
 	/* multicast addr */
 	union ipvs_sockaddr mcast_addr;
@@ -1505,9 +1485,10 @@  static struct socket *make_send_sock(struct netns_ipvs *ipvs, int id)
 				  IPPROTO_UDP, &sock);
 	if (result < 0) {
 		pr_err("Error during creation of socket; terminating\n");
-		return ERR_PTR(result);
+		goto error;
 	}
-	result = set_mcast_if(sock->sk, ipvs->mcfg.mcast_ifn);
+	*sock_ret = sock;
+	result = set_mcast_if(sock->sk, dev);
 	if (result < 0) {
 		pr_err("Error setting outbound mcast interface\n");
 		goto error;
@@ -1522,7 +1503,7 @@  static struct socket *make_send_sock(struct netns_ipvs *ipvs, int id)
 		set_sock_size(sock->sk, 1, result);
 
 	if (AF_INET == ipvs->mcfg.mcast_af)
-		result = bind_mcastif_addr(sock, ipvs->mcfg.mcast_ifn);
+		result = bind_mcastif_addr(sock, dev);
 	else
 		result = 0;
 	if (result < 0) {
@@ -1538,19 +1519,18 @@  static struct socket *make_send_sock(struct netns_ipvs *ipvs, int id)
 		goto error;
 	}
 
-	return sock;
+	return 0;
 
 error:
-	sock_release(sock);
-	return ERR_PTR(result);
+	return result;
 }
 
 
 /*
  *      Set up receiving multicast socket over UDP
  */
-static struct socket *make_receive_sock(struct netns_ipvs *ipvs, int id,
-					int ifindex)
+static int make_receive_sock(struct netns_ipvs *ipvs, int id,
+			     struct net_device *dev, struct socket **sock_ret)
 {
 	/* multicast addr */
 	union ipvs_sockaddr mcast_addr;
@@ -1562,8 +1542,9 @@  static struct socket *make_receive_sock(struct netns_ipvs *ipvs, int id,
 				  IPPROTO_UDP, &sock);
 	if (result < 0) {
 		pr_err("Error during creation of socket; terminating\n");
-		return ERR_PTR(result);
+		goto error;
 	}
+	*sock_ret = sock;
 	/* it is equivalent to the REUSEADDR option in user-space */
 	sock->sk->sk_reuse = SK_CAN_REUSE;
 	result = sysctl_sync_sock_size(ipvs);
@@ -1571,7 +1552,7 @@  static struct socket *make_receive_sock(struct netns_ipvs *ipvs, int id,
 		set_sock_size(sock->sk, 0, result);
 
 	get_mcast_sockaddr(&mcast_addr, &salen, &ipvs->bcfg, id);
-	sock->sk->sk_bound_dev_if = ifindex;
+	sock->sk->sk_bound_dev_if = dev->ifindex;
 	result = sock->ops->bind(sock, (struct sockaddr *)&mcast_addr, salen);
 	if (result < 0) {
 		pr_err("Error binding to the multicast addr\n");
@@ -1582,21 +1563,20 @@  static struct socket *make_receive_sock(struct netns_ipvs *ipvs, int id,
 #ifdef CONFIG_IP_VS_IPV6
 	if (ipvs->bcfg.mcast_af == AF_INET6)
 		result = join_mcast_group6(sock->sk, &mcast_addr.in6.sin6_addr,
-					   ipvs->bcfg.mcast_ifn);
+					   dev);
 	else
 #endif
 		result = join_mcast_group(sock->sk, &mcast_addr.in.sin_addr,
-					  ipvs->bcfg.mcast_ifn);
+					  dev);
 	if (result < 0) {
 		pr_err("Error joining to the multicast group\n");
 		goto error;
 	}
 
-	return sock;
+	return 0;
 
 error:
-	sock_release(sock);
-	return ERR_PTR(result);
+	return result;
 }
 
 
@@ -1778,13 +1758,12 @@  static int sync_thread_backup(void *data)
 int start_sync_thread(struct netns_ipvs *ipvs, struct ipvs_sync_daemon_cfg *c,
 		      int state)
 {
-	struct ip_vs_sync_thread_data *tinfo;
+	struct ip_vs_sync_thread_data *tinfo = NULL;
 	struct task_struct **array = NULL, *task;
-	struct socket *sock;
 	struct net_device *dev;
 	char *name;
 	int (*threadfn)(void *data);
-	int id, count, hlen;
+	int id = 0, count, hlen;
 	int result = -ENOMEM;
 	u16 mtu, min_mtu;
 
@@ -1792,6 +1771,18 @@  int start_sync_thread(struct netns_ipvs *ipvs, struct ipvs_sync_daemon_cfg *c,
 	IP_VS_DBG(7, "Each ip_vs_sync_conn entry needs %zd bytes\n",
 		  sizeof(struct ip_vs_sync_conn_v0));
 
+	/* Do not hold one mutex and then to block on another */
+	for (;;) {
+		rtnl_lock();
+		if (mutex_trylock(&ipvs->sync_mutex))
+			break;
+		rtnl_unlock();
+		mutex_lock(&ipvs->sync_mutex);
+		if (rtnl_trylock())
+			break;
+		mutex_unlock(&ipvs->sync_mutex);
+	}
+
 	if (!ipvs->sync_state) {
 		count = clamp(sysctl_sync_ports(ipvs), 1, IPVS_SYNC_PORTS_MAX);
 		ipvs->threads_mask = count - 1;
@@ -1810,7 +1801,8 @@  int start_sync_thread(struct netns_ipvs *ipvs, struct ipvs_sync_daemon_cfg *c,
 	dev = __dev_get_by_name(ipvs->net, c->mcast_ifn);
 	if (!dev) {
 		pr_err("Unknown mcast interface: %s\n", c->mcast_ifn);
-		return -ENODEV;
+		result = -ENODEV;
+		goto out_early;
 	}
 	hlen = (AF_INET6 == c->mcast_af) ?
 	       sizeof(struct ipv6hdr) + sizeof(struct udphdr) :
@@ -1827,26 +1819,30 @@  int start_sync_thread(struct netns_ipvs *ipvs, struct ipvs_sync_daemon_cfg *c,
 		c->sync_maxlen = mtu - hlen;
 
 	if (state == IP_VS_STATE_MASTER) {
+		result = -EEXIST;
 		if (ipvs->ms)
-			return -EEXIST;
+			goto out_early;
 
 		ipvs->mcfg = *c;
 		name = "ipvs-m:%d:%d";
 		threadfn = sync_thread_master;
 	} else if (state == IP_VS_STATE_BACKUP) {
+		result = -EEXIST;
 		if (ipvs->backup_threads)
-			return -EEXIST;
+			goto out_early;
 
 		ipvs->bcfg = *c;
 		name = "ipvs-b:%d:%d";
 		threadfn = sync_thread_backup;
 	} else {
-		return -EINVAL;
+		result = -EINVAL;
+		goto out_early;
 	}
 
 	if (state == IP_VS_STATE_MASTER) {
 		struct ipvs_master_sync_state *ms;
 
+		result = -ENOMEM;
 		ipvs->ms = kcalloc(count, sizeof(ipvs->ms[0]), GFP_KERNEL);
 		if (!ipvs->ms)
 			goto out;
@@ -1862,39 +1858,38 @@  int start_sync_thread(struct netns_ipvs *ipvs, struct ipvs_sync_daemon_cfg *c,
 	} else {
 		array = kcalloc(count, sizeof(struct task_struct *),
 				GFP_KERNEL);
+		result = -ENOMEM;
 		if (!array)
 			goto out;
 	}
 
-	tinfo = NULL;
 	for (id = 0; id < count; id++) {
-		if (state == IP_VS_STATE_MASTER)
-			sock = make_send_sock(ipvs, id);
-		else
-			sock = make_receive_sock(ipvs, id, dev->ifindex);
-		if (IS_ERR(sock)) {
-			result = PTR_ERR(sock);
-			goto outtinfo;
-		}
+		result = -ENOMEM;
 		tinfo = kmalloc(sizeof(*tinfo), GFP_KERNEL);
 		if (!tinfo)
-			goto outsocket;
+			goto out;
 		tinfo->ipvs = ipvs;
-		tinfo->sock = sock;
+		tinfo->sock = NULL;
 		if (state == IP_VS_STATE_BACKUP) {
 			tinfo->buf = kmalloc(ipvs->bcfg.sync_maxlen,
 					     GFP_KERNEL);
 			if (!tinfo->buf)
-				goto outtinfo;
+				goto out;
 		} else {
 			tinfo->buf = NULL;
 		}
 		tinfo->id = id;
+		if (state == IP_VS_STATE_MASTER)
+			result = make_send_sock(ipvs, id, dev, &tinfo->sock);
+		else
+			result = make_receive_sock(ipvs, id, dev, &tinfo->sock);
+		if (result < 0)
+			goto out;
 
 		task = kthread_run(threadfn, tinfo, name, ipvs->gen, id);
 		if (IS_ERR(task)) {
 			result = PTR_ERR(task);
-			goto outtinfo;
+			goto out;
 		}
 		tinfo = NULL;
 		if (state == IP_VS_STATE_MASTER)
@@ -1911,20 +1906,20 @@  int start_sync_thread(struct netns_ipvs *ipvs, struct ipvs_sync_daemon_cfg *c,
 	ipvs->sync_state |= state;
 	spin_unlock_bh(&ipvs->sync_buff_lock);
 
+	mutex_unlock(&ipvs->sync_mutex);
+	rtnl_unlock();
+
 	/* increase the module use count */
 	ip_vs_use_count_inc();
 
 	return 0;
 
-outsocket:
-	sock_release(sock);
-
-outtinfo:
-	if (tinfo) {
-		sock_release(tinfo->sock);
-		kfree(tinfo->buf);
-		kfree(tinfo);
-	}
+out:
+	/* We do not need RTNL lock anymore, release it here so that
+	 * sock_release below and in the kthreads can use rtnl_lock
+	 * to leave the mcast group.
+	 */
+	rtnl_unlock();
 	count = id;
 	while (count-- > 0) {
 		if (state == IP_VS_STATE_MASTER)
@@ -1932,13 +1927,23 @@  int start_sync_thread(struct netns_ipvs *ipvs, struct ipvs_sync_daemon_cfg *c,
 		else
 			kthread_stop(array[count]);
 	}
-	kfree(array);
-
-out:
 	if (!(ipvs->sync_state & IP_VS_STATE_MASTER)) {
 		kfree(ipvs->ms);
 		ipvs->ms = NULL;
 	}
+	mutex_unlock(&ipvs->sync_mutex);
+	if (tinfo) {
+		if (tinfo->sock)
+			sock_release(tinfo->sock);
+		kfree(tinfo->buf);
+		kfree(tinfo);
+	}
+	kfree(array);
+	return result;
+
+out_early:
+	mutex_unlock(&ipvs->sync_mutex);
+	rtnl_unlock();
 	return result;
 }