i40iw: Avoid panic when handling the inetdev event

There is a panic reported that on a system with x722 ethernet, when doing
the operations like:

	# ip link add br0 type bridge
	# ip link set eno1 master br0
	# systemctl restart systemd-networkd

The system will panic "BUG: unable to handle kernel null pointer
dereference at 0000000000000034", with call chain:

	i40iw_inetaddr_event
	notifier_call_chain
	blocking_notifier_call_chain
	notifier_call_chain
	__inet_del_ifa
	inet_rtm_deladdr
	rtnetlink_rcv_msg
	netlink_rcv_skb
	rtnetlink_rcv
	netlink_unicast
	netlink_sendmsg
	sock_sendmsg
	__sys_sendto

It is caused by "local_ipaddr = ntohl(in->ifa_list->ifa_address)", while
the in->ifa_list is NULL.

So add a check for the "in->ifa_list == NULL" case, and skip the ARP
operation accordingly.

Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

diff --git a/drivers/infiniband/hw/i40iw/i40iw_utils.c b/drivers/infiniband/hw/i40iw/i40iw_utils.c
index c5a8811..337410f 100644 (file)
--- a/drivers/infiniband/hw/i40iw/i40iw_utils.c
+++ b/drivers/infiniband/hw/i40iw/i40iw_utils.c
@@ -173,7 +173,12 @@ int i40iw_inetaddr_event(struct notifier_block *notifier,
 
                rcu_read_lock();
                in = __in_dev_get_rcu(upper_dev);
-               local_ipaddr = ntohl(in->ifa_list->ifa_address);
+
+               if (!in->ifa_list)
+                       local_ipaddr = 0;
+               else
+                       local_ipaddr = ntohl(in->ifa_list->ifa_address);
+
                rcu_read_unlock();
        } else {
                local_ipaddr = ntohl(ifa->ifa_address);
@@ -185,6 +190,11 @@ int i40iw_inetaddr_event(struct notifier_block *notifier,
        case NETDEV_UP:
                /* Fall through */
        case NETDEV_CHANGEADDR:
+
+               /* Just skip if no need to handle ARP cache */
+               if (!local_ipaddr)
+                       break;
+
                i40iw_manage_arp_cache(iwdev,
                                       netdev->dev_addr,
                                       &local_ipaddr,