macvlan: Don't propagate promisc change to lower dev in passthru

Macvlan device in passthru mode sets its lower device promiscuous mode
according to its MACVLAN_FLAG_NOPROMISC flag instead of synchronizing it to
its own promiscuity setting. However, macvlan_change_rx_flags() function
doesn't check the mode before propagating such changes to the lower device
which can cause net_device->promiscuity counter overflow as illustrated by
reproduction example [0] and resulting dmesg log [1]. Fix the issue by
first verifying the mode in macvlan_change_rx_flags() function before
propagating promiscuous mode change to the lower device.

[0]:
ip link add macvlan1 link enp8s0f0 type macvlan mode passthru
ip link set macvlan1 promisc on
ip l set dev macvlan1 up
ip link set macvlan1 promisc off
ip l set dev macvlan1 down
ip l set dev macvlan1 up

[1]:
[ 5156.281724] macvlan1: entered promiscuous mode
[ 5156.285467] mlx5_core 0000:08:00.0 enp8s0f0: entered promiscuous mode
[ 5156.287639] macvlan1: left promiscuous mode
[ 5156.288339] mlx5_core 0000:08:00.0 enp8s0f0: left promiscuous mode
[ 5156.290907] mlx5_core 0000:08:00.0 enp8s0f0: entered promiscuous mode
[ 5156.317197] mlx5_core 0000:08:00.0 enp8s0f0: promiscuity touches roof, set promiscuity failed. promiscuity feature of device might be broken.

Fixes: efdbd2b ("macvlan: Propagate promiscuity setting to lower devices.")
Reviewed-by: Gal Pressman <[email protected]>
Signed-off-by: Vlad Buslov <[email protected]>
Reviewed-by: Jiri Pirko <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

Author: w1ldptr

drivers/net/macvlan.c

@@ -780,7 +780,7 @@ static void macvlan_change_rx_flags(struct net_device *dev, int change)
 	if (dev->flags & IFF_UP) {
 		if (change & IFF_ALLMULTI)
 			dev_set_allmulti(lowerdev, dev->flags & IFF_ALLMULTI ? 1 : -1);
-		if (change & IFF_PROMISC)
+		if (!macvlan_passthru(vlan->port) && change & IFF_PROMISC)
 			dev_set_promiscuity(lowerdev,
 					    dev->flags & IFF_PROMISC ? 1 : -1);