AZL-62501

In the Linux kernel, the following vulnerability has been resolved:

net: fix NULL pointer dereference in l3mdevl3rcv

When delete l3s ipvlan:

ip link del link eth0 ipvlan1 type ipvlan mode l3s

This may cause a null pointer dereference:

Call trace:
 ip_rcv_finish+0x48/0xd0
 ip_rcv+0x5c/0x100
 __netif_receive_skb_one_core+0x64/0xb0
 __netif_receive_skb+0x20/0x80
 process_backlog+0xb4/0x204
 napi_poll+0xe8/0x294
 net_rx_action+0xd8/0x22c
 __do_softirq+0x12c/0x354

This is because l3mdevl3rcv() visit dev->l3mdevops after ipvlanl3sunregister() assign the dev->l3mdevops to NULL. The process like this:

(CPU1)                     | (CPU2)
l3mdev_l3_rcv()            |
  check dev->priv_flags:   |
    master = skb->dev;     |
                           |
                           | ipvlan_l3s_unregister()
                           |   set dev->priv_flags
                           |   dev->l3mdev_ops = NULL;
                           |
  visit master->l3mdev_ops |

To avoid this by do not set dev->l3mdev_ops when unregister l3s ipvlan.