[PATCH net] net: hsr: fix memory leak on slave unregistration by removing synced VLANs

[Eric Dumazet <edumazet@google.com>]

When an HSR master device is brought UP, it auto-adds VLAN 0 via
vlan_vid0_add(), which propagates VID 0 to its slave devices.

If a slave device is later unregistered while HSR is active (e.g., during
netns cleanup or interface destruction), hsr_del_port() is called to
detach the slave port from the HSR master. However, hsr_del_port() currently
does not delete the VLAN IDs that were synced to the slave device by HSR.

As a result, the slave device retains a refcount on VID 0 (and any other
synced VLANs). When the slave device is destroyed, its vlan_info /
vlan_vid_info structure remains allocated, leading to a memory leak.

Fix this by calling vlan_vids_del_by_dev(port->dev, master->dev) in
hsr_del_port() before unlinking the slave device, matching the cleanup
behavior in bonding and team drivers.

Fixes: 1a8a63a5305e ("net: hsr: Add VLAN CTAG filter support")
Reported-by: syzbot+456957213f32970c0762@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/6a4cb6ca.57639fcc.86d58.000b.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/hsr/hsr_slave.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/hsr/hsr_slave.c b/net/hsr/hsr_slave.c
index d9af9e65f72f07b1997b80c85db16d812fbda488..2d1e3ea72088e35d5d870b4cc86dd2f789670394 100644
--- a/net/hsr/hsr_slave.c
+++ b/net/hsr/hsr_slave.c
@@ -242,6 +242,7 @@ void hsr_del_port(struct hsr_port *port)
 		netdev_rx_handler_unregister(port->dev);
 		if (!port->hsr->fwd_offloaded)
 			dev_set_promiscuity(port->dev, -1);
+		vlan_vids_del_by_dev(port->dev, master->dev);
 		netdev_upper_dev_unlink(port->dev, master->dev);
 		if (hsr->prot_version == PRP_V1 &&
 		    port->type == HSR_PT_SLAVE_B) {
-- 
2.55.0.795.g602f6c329a-goog