[PATCH net] vlan: Fix to delete vid only when by_dev has hw filter capable in vlan_vids_del_by_dev()

[Ziyang Xuan <william.xuanziyang@huawei.com>]

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() // allocate vlan_info for bond_slave_1
    __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 vlan_hw_filter_capable() check for by_dev when delete vids in
vlan_vids_del_by_dev() to fix the bug.

Fixes: 8ad227ff89a7 ("net: vlan: add 802.1ad support")
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
---
 net/8021q/vlan_core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
index 0beb44f2fe1f..79cf4f033b66 100644
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -436,8 +436,11 @@ void vlan_vids_del_by_dev(struct net_device *dev,
 	if (!vlan_info)
 		return;
 
-	list_for_each_entry(vid_info, &vlan_info->vid_list, list)
+	list_for_each_entry(vid_info, &vlan_info->vid_list, list) {
+		if (!vlan_hw_filter_capable(by_dev, vid_info->proto))
+			continue;
 		vlan_vid_del(dev, vid_info->proto, vid_info->vid);
+	}
 }
 EXPORT_SYMBOL(vlan_vids_del_by_dev);
 
-- 
2.25.1