Created attachment 274725 [details] journalctl -k --no-hostname --no-pager output I'm consistently getting this kernel NULL pointer dereference on a Thecus N5550 NAS box (Intel Atom D2550 CPU) on every boot if gma500_gfx module is not blacklisted: Mar 14 13:44:02 kernel: BUG: unable to handle kernel NULL pointer dereference at 0000000000000081 Mar 14 13:44:02 kernel: IP: drm_fb_helper_is_bound.isra.16+0x5/0xa0 [drm_kms_helper] Mar 14 13:44:03 kernel: PGD 0 P4D 0 Mar 14 13:44:03 kernel: Oops: 0000 [#1] SMP NOPTI Mar 14 13:44:03 kernel: Modules linked in: it87 hwmon_vid vfat fat snd_hda_codec_realtek snd_hda_codec_generic gma500_gfx snd_hda_codec_hdmi iTCO_wdt iTCO_vendor_support snd Mar 14 13:44:03 kernel: CPU: 0 PID: 277 Comm: kworker/0:2 Not tainted 4.15.7-300.fc27.x86_64 #1 Mar 14 13:44:03 kernel: Hardware name: Intel Corporation Milstead Platform/Granite Well, BIOS CDV_T30 X64 09/17/2012 Mar 14 13:44:03 kernel: Workqueue: events output_poll_execute [drm_kms_helper] Mar 14 13:44:03 kernel: RIP: 0010:drm_fb_helper_is_bound.isra.16+0x5/0xa0 [drm_kms_helper] Mar 14 13:44:03 kernel: RSP: 0018:ffffb118005ebe28 EFLAGS: 00010286 Mar 14 13:44:03 kernel: RAX: 0000000000000000 RBX: ffff9da9b656c800 RCX: 000000000000e800 Mar 14 13:44:03 kernel: RDX: ffff9da9b632da00 RSI: 0000000000000031 RDI: ffff9da9b656c800 Mar 14 13:44:03 kernel: RBP: ffff9da9b656c8d0 R08: 00000000000251a0 R09: 0000000000000000 Mar 14 13:44:03 kernel: R10: fffff2ca40f61c00 R11: 0000000000000000 R12: 0000000000000001 Mar 14 13:44:03 kernel: R13: ffff9da9b71e7800 R14: ffff9da9b71e79f8 R15: 0000000000000000 Mar 14 13:44:03 kernel: FS: 0000000000000000(0000) GS:ffff9da9bb400000(0000) knlGS:0000000000000000 Mar 14 13:44:03 kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Mar 14 13:44:03 kernel: CR2: 0000000000000081 CR3: 000000007b2a0000 CR4: 00000000000006f0 Mar 14 13:44:03 kernel: Call Trace: Mar 14 13:44:03 kernel: drm_fb_helper_hotplug_event.part.29+0x34/0xb0 [drm_kms_helper] Mar 14 13:44:03 kernel: output_poll_execute+0x185/0x1b0 [drm_kms_helper] Mar 14 13:44:03 kernel: process_one_work+0x175/0x390 Mar 14 13:44:03 kernel: worker_thread+0x2e/0x380 Mar 14 13:44:03 kernel: ? process_one_work+0x390/0x390 Mar 14 13:44:03 kernel: kthread+0x113/0x130 Mar 14 13:44:03 kernel: ? kthread_create_worker_on_cpu+0x70/0x70 Mar 14 13:44:03 kernel: ret_from_fork+0x1f/0x40 Mar 14 13:44:03 kernel: Code: 4c d0 f8 8b 45 20 39 c3 7c e6 83 e8 01 4c 89 ef 31 db 89 45 20 e8 6c b0 ea c4 eb 9f 83 c3 02 eb bf 0f 1f 44 00 00 0f 1f 44 00 00 <48> 8b 56 50 Mar 14 13:44:03 kernel: RIP: drm_fb_helper_is_bound.isra.16+0x5/0xa0 [drm_kms_helper] RSP: ffffb118005ebe28 Mar 14 13:44:03 kernel: CR2: 0000000000000081 Mar 14 13:44:03 kernel: ---[ end trace 0bc03676f9e43f5d ]--- Full dmesg attached.
Looks like this is no longer occurring in 4.17.2 (Fedora 28). I haven't checked if the actual video output still works after unblacklisting the gma500_gfx driver, but at least it's no longer trying to do a NULL pointer dereference. I don't have time to do a bisect to see which commit fixed it, sadly.
As discussed in https://bugs.freedesktop.org/show_bug.cgi?id=106470, gfx are working on the Thecus N5550 NAS now, so this can be closed. The only remaining issue is the gma500 driver thinking there is an LVDS panel, this can be worked around by passing: "video=LVDS-1:d" on the kernel commandline. Fixing the LVDS issue properly (with a DMI based blacklist) is being tracked here: https://bugzilla.redhat.com/show_bug.cgi?id=1665766