net: fix stack overflow when LRO is disabled for virtual interfaces

When the virtual interface's feature is updated, it synchronizes the
updated feature for its own lower interface.
This propagation logic should be worked as the iteration, not recursively.
But it works recursively due to the netdev notification unexpectedly.
This problem occurs when it disables LRO only for the team and bonding
interface type.

       team0
         |
  +------+------+-----+-----+
  |      |      |     |     |
team1  team2  team3  ...  team200

If team0's LRO feature is updated, it generates the NETDEV_FEAT_CHANGE
event to its own lower interfaces(team1 ~ team200).
It is worked by netdev_sync_lower_features().
So, the NETDEV_FEAT_CHANGE notification logic of each lower interface
work iteratively.
But generated NETDEV_FEAT_CHANGE event is also sent to the upper
interface too.
upper interface(team0) generates the NETDEV_FEAT_CHANGE event for its own
lower interfaces again.
lower and upper interfaces receive this event and generate this
event again and again.
So, the stack overflow occurs.

But it is not the infinite loop issue.
Because the netdev_sync_lower_features() updates features before
generating the NETDEV_FEAT_CHANGE event.
Already synchronized lower interfaces skip notification logic.
So, it is just the problem that iteration logic is changed to the
recursive unexpectedly due to the notification mechanism.

Reproducer:

ip link add team0 type team
ethtool -K team0 lro on
for i in {1..200}
do
        ip link add team$i master team0 type team
        ethtool -K team$i lro on
done

ethtool -K team0 lro off

In order to fix it, the notifier_ctx member of bonding/team is introduced.

Reported-by: syzbot+60748c96cf5c6df8e581@syzkaller.appspotmail.com
Fixes: fd867d51 ("net/core: generic support for disabling netdev features down stack")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://lore.kernel.org/r/20230517143010.3596250-1-ap420073@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/bonding/bond_main.c

@@ -3947,7 +3947,11 @@ static int bond_slave_netdev_event(unsigned long event,
 		unblock_netpoll_tx();
 		break;
 	case NETDEV_FEAT_CHANGE:
-		bond_compute_features(bond);
+		if (!bond->notifier_ctx) {
+			bond->notifier_ctx = true;
+			bond_compute_features(bond);
+			bond->notifier_ctx = false;
+		}
 		break;
 	case NETDEV_RESEND_IGMP:
 		/* Propagate to master device */
@@ -6342,6 +6346,8 @@ static int bond_init(struct net_device *bond_dev)
 	if (!bond->wq)
 		return -ENOMEM;
 
+	bond->notifier_ctx = false;
+
 	spin_lock_init(&bond->stats_lock);
 	netdev_lockdep_set_classes(bond_dev);
 

drivers/net/team/team.c

@@ -1629,6 +1629,7 @@ static int team_init(struct net_device *dev)
 
 	team->dev = dev;
 	team_set_no_mode(team);
+	team->notifier_ctx = false;
 
 	team->pcpu_stats = netdev_alloc_pcpu_stats(struct team_pcpu_stats);
 	if (!team->pcpu_stats)
@@ -3022,7 +3023,11 @@ static int team_device_event(struct notifier_block *unused,
 		team_del_slave(port->team->dev, dev);
 		break;
 	case NETDEV_FEAT_CHANGE:
-		team_compute_features(port->team);
+		if (!port->team->notifier_ctx) {
+			port->team->notifier_ctx = true;
+			team_compute_features(port->team);
+			port->team->notifier_ctx = false;
+		}
 		break;
 	case NETDEV_PRECHANGEMTU:
 		/* Forbid to change mtu of underlaying device */

include/linux/if_team.h

@@ -208,6 +208,7 @@ struct team {
 	bool queue_override_enabled;
 	struct list_head *qom_lists; /* array of queue override mapping lists */
 	bool port_mtu_change_allowed;
+	bool notifier_ctx;
 	struct {
 		unsigned int count;
 		unsigned int interval; /* in ms */

include/net/bonding.h

@@ -221,6 +221,7 @@ struct bonding {
 	struct   bond_up_slave __rcu *usable_slaves;
 	struct   bond_up_slave __rcu *all_slaves;
 	bool     force_primary;
+	bool     notifier_ctx;
 	s32      slave_cnt; /* never change this value outside the attach/detach wrappers */
 	int     (*recv_probe)(const struct sk_buff *, struct bonding *,
 			      struct slave *);