The same thing happens on dock disconnect with Lenovo Thinkpad T480. Here is the log. Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224084] BUG: unable to handle kernel NULL pointer dereference at 0000000000000245 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224110] IP: intel_ddi_post_disable+0x54/0x170 [i915] Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224111] PGD 0 P4D 0 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224113] Oops: 0000 [#1] SMP PTI Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224115] Modules linked in: ax88179_178a usbnet mii hid_generic usbhid hid rfcomm snd_hrtimer cmac bnep binfmt_misc nls_iso8859_1 arc4 snd_soc_skl snd_hda_codec_hdmi snd_soc_skl_ipc snd_hda_ext_core snd_soc_sst_dsp snd_soc_sst_ipc snd_hda_codec_realtek snd_soc_acpi iwlmvm snd_hda_codec_generic snd_soc_core snd_compress intel_rapl ac97_bus snd_pcm_dmaengine mac80211 x86_pkg_temp_thermal intel_powerclamp coretemp uvcvideo snd_hda_intel videobuf2_vmalloc videobuf2_memops kvm_intel snd_hda_codec videobuf2_v4l2 snd_hda_core videobuf2_core snd_hwdep kvm videodev snd_pcm media irqbypass btusb intel_cstate btrtl iwlwifi btbcm btintel intel_rapl_perf joydev input_leds bluetooth snd_seq_midi snd_seq_midi_event serio_raw ucsi_acpi snd_rawmidi typec_ucsi cfg80211 ecdh_generic wmi_bmof intel_wmi_thunderbolt Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224142] typec snd_seq thinkpad_acpi nvram int3403_thermal snd_seq_device snd_timer processor_thermal_device snd int340x_thermal_zone intel_pch_thermal mei_me soundcore mei intel_soc_dts_iosf mac_hid acpi_pad int3400_thermal shpchp acpi_thermal_rel sch_fq_codel cuse parport_pc ppdev lp parport sunrpc ip_tables x_tables autofs4 algif_skcipher af_alg dm_crypt raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear dm_mirror dm_region_hash dm_log crct10dif_pclmul crc32_pclmul ghash_clmulni_intel uas usb_storage pcbc i915 aesni_intel aes_x86_64 crypto_simd i2c_algo_bit glue_helper cryptd drm_kms_helper e1000e syscopyarea psmouse sysfillrect sysimgblt nvme ptp fb_sys_fops i2c_i801 pps_core nvme_core thunderbolt drm wmi video Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224174] CPU: 0 PID: 59 Comm: kworker/0:1 Not tainted 4.15.0-44-generic #47-Ubuntu Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224175] Hardware name: LENOVO 20L6S93F00/20L6S93F00, BIOS N24ET41W (1.16 ) 07/18/2018 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224186] Workqueue: events drm_mode_rmfb_work_fn [drm] Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224203] RIP: 0010:intel_ddi_post_disable+0x54/0x170 [i915] Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224204] RSP: 0018:ffffb62e81b47be8 EFLAGS: 00010297 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224205] RAX: 0000000000000007 RBX: ffff9834d0826000 RCX: ffffffffc08f5272 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224206] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff9834d0826000 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224207] RBP: ffffb62e81b47c18 R08: ffffffffffffff80 R09: 00000000000000ff Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224208] R10: ffff9834cf5e2998 R11: ffff9834cf5e2988 R12: 0000000000000000 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224209] R13: ffff9834d0826000 R14: ffff9834cf5e0000 R15: ffff9834d7e07000 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224211] FS: 0000000000000000(0000) GS:ffff9834ef400000(0000) knlGS:0000000000000000 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224212] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224213] CR2: 0000000000000245 CR3: 0000000250c0a001 CR4: 00000000003606f0 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224214] Call Trace: Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224229] ? intel_dp_sink_dpms+0x87/0xf0 [i915] Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224243] intel_mst_post_disable_dp+0x99/0xd0 [i915] Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224257] intel_encoders_post_disable.isra.102+0x66/0x80 [i915] Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224270] haswell_crtc_disable+0xe8/0x150 [i915] Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224283] intel_atomic_commit_tail+0x7ea/0xd30 [i915] Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224295] intel_atomic_commit+0x277/0x2b0 [i915] Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224303] drm_atomic_commit+0x51/0x60 [drm] Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224310] drm_framebuffer_remove+0x29e/0x3b0 [drm] Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224316] drm_mode_rmfb_work_fn+0x41/0x50 [drm] Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224318] process_one_work+0x1de/0x410 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224320] worker_thread+0x228/0x410 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224322] kthread+0x121/0x140 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224324] ? process_one_work+0x410/0x410 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224326] ? kthread_create_worker_on_cpu+0x70/0x70 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224328] ret_from_fork+0x35/0x40 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224329] Code: 0d f6 86 44 02 00 00 40 0f 85 81 00 00 00 83 f8 06 72 77 83 f8 08 76 13 83 f8 0a 75 6d 41 f6 86 60 06 00 00 40 0f 84 dd 00 00 00 <41> f6 84 24 45 02 00 00 08 4d 8d bd 00 01 00 00 74 3e 48 89 df Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224364] RIP: intel_ddi_post_disable+0x54/0x170 [i915] RSP: ffffb62e81b47be8 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224364] CR2: 0000000000000245 Jan 30 17:42:46 cubbli18-gold kernel: [ 169.224366] ---[ end trace ef48086275e9619e ]---