System panic when Intel 710 series (i40e) interface goes down with: BUG: unable to handle kernel NULL pointer dereference at 00000000000001c0 at i40e_client_get_params+0x69/0xc0

Issue

• A RHEL system using i40e may crash when link state changes with a backtrace similar to the following. The backtrace shows i40e in the i40e_handle_lldp_event() function:

  [   36.081433] BUG: unable to handle kernel NULL pointer dereference at 00000000000001c0
  [   36.081676] IP: [<ffffffffa04f9409>] i40e_client_get_params+0x69/0xc0 [i40e]
  [   36.081846] PGD 4692021067 PUD 469dd35067 PMD 0 
  [   36.082159] Oops: 0000 [#1] SMP 
  [   36.082394] Modules linked in: nfsv3 rpcsec_gss_krb5 nfsv4 dns_resolver nfs fscache bonding dcdbas dm_service_time coretemp kvm crc32_pclmul     ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd pcspkr ses enclosure i40e sg vxlan ip6_udp_tunnel udp_tunnel ipmi_ssif i2c_core shpchp ipmi_si ipmi_msghandler acpi_power_meter acpi_pad dm_multipath nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs libcrc32c sd_mod crc_t10dif crct10dif_generic crct10dif_pclmul crct10dif_common crc32c_intel qla2xxx ixgbe scsi_transport_fc mdio scsi_tgt ahci ptp libahci pps_core megaraid_sas dca libata dm_mirror dm_region_hash dm_log dm_mod
  [   36.087678] CPU: 0 PID: 1675 Comm: kworker/u896:2 Tainted: G           O   ------------   3.10.0-327.36.3.el7.x86_64 #1
  [   36.087771] Hardware name: Dell Inc. PowerEdge R640/0W23H8, BIOS 1.3.7 02/08/2018
  [   36.087862] Workqueue: i40e i40e_service_task [i40e]
  [   36.088023] task: ffff88469be89700 ti: ffff88469b824000 task.ti: ffff88469b824000
  [   36.088228] RIP: 0010:[<ffffffffa04f9409>]  [<ffffffffa04f9409>] i40e_client_get_params+0x69/0xc0 [i40e]
  [   36.088632] RSP: 0018:ffff88469b827be8  EFLAGS: 00010246
  [   36.088833] RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000
  [   36.089036] RDX: 0000000000000000 RSI: ffff88469b827bf6 RDI: ffff884697505000
  [   36.089240] RBP: ffff88469b827c30 R08: 0000000000000005 R09: 0000000000000000
  [   36.089445] R10: 0000000000000000 R11: ffff884691cd340c R12: ffff884697505000
  [   36.089649] R13: ffff884691cd3008 R14: ffff884697505000 R15: ffff884691cd3000
  [   36.089854] FS:  0000000000000000(0000) GS:ffff88471da00000(0000) knlGS:0000000000000000
  [   36.090176] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [   36.090378] CR2: 00000000000001c0 CR3: 000000469dd68000 CR4: 00000000003407f0
  [   36.090582] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  [   36.090787] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  [   36.090990] Stack:
  [   36.091187]  ffffffffa04f9e8a 0005000000000000 0005000000050000 0005000000050000
  [   36.091821]  0005000000050000 0000000000050000 00000000a587bf3f 0000000000000001
  [   36.092455]  0000000000000001 ffff88469b827d60 ffffffffa04df09e ffff884691cd3df0
  [   36.093089] Call Trace:
  [   36.093292]  [<ffffffffa04f9e8a>] ? i40e_notify_client_of_l2_param_changes+0x5a/0x170 [i40e]
  [   36.093620]  [<ffffffffa04df09e>] i40e_handle_lldp_event+0x3de/0x740 [i40e]
  [   36.093828]  [<ffffffffa04e04ae>] i40e_service_task+0xc8e/0x1530 [i40e]
  [   36.094036]  [<ffffffff810c22de>] ? dequeue_task_fair+0x42e/0x640
  [   36.094243]  [<ffffffff8109d69b>] process_one_work+0x17b/0x470
  [   36.094448]  [<ffffffff8109e46b>] worker_thread+0x11b/0x400
  [   36.094653]  [<ffffffff8109e350>] ? rescuer_thread+0x400/0x400
  [   36.094860]  [<ffffffff810a5b8f>] kthread+0xcf/0xe0
  [   36.095063]  [<ffffffff810a5ac0>] ? kthread_create_on_node+0x140/0x140
  [   36.095272]  [<ffffffff81646a98>] ret_from_fork+0x58/0x90
  [   36.095477]  [<ffffffff810a5ac0>] ? kthread_create_on_node+0x140/0x140
  [   36.095680] Code: 44 c9 4c 63 c2 46 0f b7 84 47 7c 05 00 00 88 4c 86 02 66 41 83 f8 ff 66 44 89 04 86 74 24 48 83 c0 01 48 83 f8 08 75 ba 48 8b 07 <8b> 80 c0 01 00 00 66 89 46 20 31 c0 c3 66 2e 0f 1f 84 00 00 00 
  [   36.101105] RIP  [<ffffffffa04f9409>] i40e_client_get_params+0x69/0xc0 [i40e]
  [   36.101387]  RSP <ffff88469b827be8>
  [   36.101586] CR2: 00000000000001c0