Re: [PATCH net v2] bonding: Fix incorrect deletion of ETH_P_8021AD protocol vid from slaves

[Ido Schimmel <idosch@idosch.org>]

On Wed, Aug 02, 2023 at 07:43:20PM +0800, Ziyang Xuan wrote:
> BUG_ON(!vlan_info) is triggered in unregister_vlan_dev() with
> following testcase:
> 
>   # ip netns add ns1
>   # ip netns exec ns1 ip link add bond0 type bond mode 0
>   # ip netns exec ns1 ip link add bond_slave_1 type veth peer veth2
>   # ip netns exec ns1 ip link set bond_slave_1 master bond0
>   # ip netns exec ns1 ip link add link bond_slave_1 name vlan10 type vlan id 10 protocol 802.1ad
>   # ip netns exec ns1 ip link add link bond0 name bond0_vlan10 type vlan id 10 protocol 802.1ad
>   # ip netns exec ns1 ip link set bond_slave_1 nomaster
>   # ip netns del ns1
> 
> The logical analysis of the problem is as follows:
> 
> 1. create ETH_P_8021AD protocol vlan10 for bond_slave_1:
> register_vlan_dev()
>   vlan_vid_add()
>     vlan_info_alloc()
>     __vlan_vid_add() // add [ETH_P_8021AD, 10] vid to bond_slave_1
> 
> 2. create ETH_P_8021AD protocol bond0_vlan10 for bond0:
> register_vlan_dev()
>   vlan_vid_add()
>     __vlan_vid_add()
>       vlan_add_rx_filter_info()
>           if (!vlan_hw_filter_capable(dev, proto)) // condition established because bond0 without NETIF_F_HW_VLAN_STAG_FILTER
>               return 0;
> 
>           if (netif_device_present(dev))
>               return dev->netdev_ops->ndo_vlan_rx_add_vid(dev, proto, vid); // will be never called
>               // The slaves of bond0 will not refer to the [ETH_P_8021AD, 10] vid.
> 
> 3. detach bond_slave_1 from bond0:
> __bond_release_one()
>   vlan_vids_del_by_dev()
>     list_for_each_entry(vid_info, &vlan_info->vid_list, list)
>         vlan_vid_del(dev, vid_info->proto, vid_info->vid);
>         // bond_slave_1 [ETH_P_8021AD, 10] vid will be deleted.
>         // bond_slave_1->vlan_info will be assigned NULL.
> 
> 4. delete vlan10 during delete ns1:
> default_device_exit_batch()
>   dev->rtnl_link_ops->dellink() // unregister_vlan_dev() for vlan10
>     vlan_info = rtnl_dereference(real_dev->vlan_info); // real_dev of vlan10 is bond_slave_1
> 	BUG_ON(!vlan_info); // bond_slave_1->vlan_info is NULL now, bug is triggered!!!
> 
> Add S-VLAN tag related features support to bond driver. So the bond driver
> will always propagate the VLAN info to its slaves.
> 
> Fixes: 8ad227ff89a7 ("net: vlan: add 802.1ad support")
> Suggested-by: Ido Schimmel <idosch@idosch.org>
> Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>

Reviewed-by: Ido Schimmel <idosch@nvidia.com>