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

[Felix Maurer <fmaurer@redhat.com>]

On Tue, Jul 07, 2026 at 08:23:27AM +0000, Eric Dumazet wrote:
> 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>

Looks good to me, thank you!

Reviewed-by: Felix Maurer <fmaurer@redhat.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
>