Merge branch 'bonding-remove-rtnl-from-three-sysfs-files'

Eric Dumazet says:

====================
bonding: remove RTNL from three sysfs files

First patch might fix a potential deadlock.
sysfs handlers should use rtnl_trylock() instead of rtnl_lock().

Following files can be read without acquiring RTNL :

- /sys/class/net/bonding_masters
- /sys/class/net/<name>/bonding/slaves
- /sys/class/net/<name>/bonding/queue_id
====================

Link: https://lore.kernel.org/r/20240408190437.2214473-1-edumazet@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/bonding/bond_main.c

@@ -5245,7 +5245,7 @@ static inline int bond_slave_override(struct bonding *bond,
 
 	/* Find out if any slaves have the same mapping as this skb. */
 	bond_for_each_slave_rcu(bond, slave, iter) {
-		if (slave->queue_id == skb_get_queue_mapping(skb)) {
+		if (READ_ONCE(slave->queue_id) == skb_get_queue_mapping(skb)) {
 			if (bond_slave_is_up(slave) &&
 			    slave->link == BOND_LINK_UP) {
 				bond_dev_queue_xmit(bond, skb, slave->dev);
@@ -5933,7 +5933,7 @@ static void bond_uninit(struct net_device *bond_dev)
 
 	bond_set_slave_arr(bond, NULL, NULL);
 
-	list_del(&bond->bond_list);
+	list_del_rcu(&bond->bond_list);
 
 	bond_debug_unregister(bond);
 }
@@ -6347,7 +6347,7 @@ static int bond_init(struct net_device *bond_dev)
 	spin_lock_init(&bond->stats_lock);
 	netdev_lockdep_set_classes(bond_dev);
 
-	list_add_tail(&bond->bond_list, &bn->dev_list);
+	list_add_tail_rcu(&bond->bond_list, &bn->dev_list);
 
 	bond_prepare_sysfs_group(bond);
 

drivers/net/bonding/bond_netlink.c

@@ -51,7 +51,8 @@ static int bond_fill_slave_info(struct sk_buff *skb,
 		    slave_dev->addr_len, slave->perm_hwaddr))
 		goto nla_put_failure;
 
-	if (nla_put_u16(skb, IFLA_BOND_SLAVE_QUEUE_ID, slave->queue_id))
+	if (nla_put_u16(skb, IFLA_BOND_SLAVE_QUEUE_ID,
+			READ_ONCE(slave->queue_id)))
 		goto nla_put_failure;
 
 	if (nla_put_s32(skb, IFLA_BOND_SLAVE_PRIO, slave->prio))

drivers/net/bonding/bond_options.c

@@ -1589,7 +1589,7 @@ static int bond_option_queue_id_set(struct bonding *bond,
 		goto err_no_cmd;
 
 	/* Actually set the qids for the slave */
-	update_slave->queue_id = qid;
+	WRITE_ONCE(update_slave->queue_id, qid);
 
 out:
 	return ret;

drivers/net/bonding/bond_procfs.c

@@ -209,7 +209,7 @@ static void bond_info_show_slave(struct seq_file *seq,
 
 	seq_printf(seq, "Permanent HW addr: %*phC\n",
 		   slave->dev->addr_len, slave->perm_hwaddr);
-	seq_printf(seq, "Slave queue ID: %d\n", slave->queue_id);
+	seq_printf(seq, "Slave queue ID: %d\n", READ_ONCE(slave->queue_id));
 
 	if (BOND_MODE(bond) == BOND_MODE_8023AD) {
 		const struct port *port = &SLAVE_AD_INFO(slave)->port;

drivers/net/bonding/bond_sysfs.c

@@ -37,12 +37,12 @@ static ssize_t bonding_show_bonds(const struct class *cls,
 {
 	const struct bond_net *bn =
 		container_of_const(attr, struct bond_net, class_attr_bonding_masters);
-	int res = 0;
 	struct bonding *bond;
+	int res = 0;
 
-	rtnl_lock();
+	rcu_read_lock();
 
-	list_for_each_entry(bond, &bn->dev_list, bond_list) {
+	list_for_each_entry_rcu(bond, &bn->dev_list, bond_list) {
 		if (res > (PAGE_SIZE - IFNAMSIZ)) {
 			/* not enough space for another interface name */
 			if ((PAGE_SIZE - res) > 10)
@@ -55,7 +55,7 @@ static ssize_t bonding_show_bonds(const struct class *cls,
 	if (res)
 		buf[res-1] = '\n'; /* eat the leftover space */
 
-	rtnl_unlock();
+	rcu_read_unlock();
 	return res;
 }
 
@@ -170,10 +170,9 @@ static ssize_t bonding_show_slaves(struct device *d,
 	struct slave *slave;
 	int res = 0;
 
-	if (!rtnl_trylock())
-		return restart_syscall();
+	rcu_read_lock();
 
-	bond_for_each_slave(bond, slave, iter) {
+	bond_for_each_slave_rcu(bond, slave, iter) {
 		if (res > (PAGE_SIZE - IFNAMSIZ)) {
 			/* not enough space for another interface name */
 			if ((PAGE_SIZE - res) > 10)
@@ -184,7 +183,7 @@ static ssize_t bonding_show_slaves(struct device *d,
 		res += sysfs_emit_at(buf, res, "%s ", slave->dev->name);
 	}
 
-	rtnl_unlock();
+	rcu_read_unlock();
 
 	if (res)
 		buf[res-1] = '\n'; /* eat the leftover space */
@@ -626,10 +625,9 @@ static ssize_t bonding_show_queue_id(struct device *d,
 	struct slave *slave;
 	int res = 0;
 
-	if (!rtnl_trylock())
-		return restart_syscall();
+	rcu_read_lock();
 
-	bond_for_each_slave(bond, slave, iter) {
+	bond_for_each_slave_rcu(bond, slave, iter) {
 		if (res > (PAGE_SIZE - IFNAMSIZ - 6)) {
 			/* not enough space for another interface_name:queue_id pair */
 			if ((PAGE_SIZE - res) > 10)
@@ -638,12 +636,13 @@ static ssize_t bonding_show_queue_id(struct device *d,
 			break;
 		}
 		res += sysfs_emit_at(buf, res, "%s:%d ",
-				     slave->dev->name, slave->queue_id);
+				     slave->dev->name,
+				     READ_ONCE(slave->queue_id));
 	}
 	if (res)
 		buf[res-1] = '\n'; /* eat the leftover space */
 
-	rtnl_unlock();
+	rcu_read_unlock();
 
 	return res;
 }

drivers/net/bonding/bond_sysfs_slave.c

@@ -53,7 +53,7 @@ static SLAVE_ATTR_RO(perm_hwaddr);
 
 static ssize_t queue_id_show(struct slave *slave, char *buf)
 {
-	return sysfs_emit(buf, "%d\n", slave->queue_id);
+	return sysfs_emit(buf, "%d\n", READ_ONCE(slave->queue_id));
 }
 static SLAVE_ATTR_RO(queue_id);