Unexpected reboot – MT7921 UBSAN kernel bug + AMD GPU black screen`

Ask Fedora
, ,
1

System:

  • Kernel: 7.2.5-200.fc44.x86_64
  • GPU: AMD (amdgpu driver)
  • WLAN: MediaTek MT7921
  • Filesystem: Btrfs (behind LUKS encryption)
  • Desktop: GNOME

Problem:

My machine unexpectedly rebooted without any user interaction. The sequence was: screen went black → BIOS boot screen appeared → black again → automatic reboot. No clean shutdown, no visible error message on screen.

What the logs show:

The reboot was most likely triggered by a kernel bug in the MT7921 wireless driver, occurring at boot time:

kernel: UBSAN: array-index-out-of-bounds in drivers/net/wireless/mediatek/mt76/mt7921/mcu.c:471:15
kernel: index 3 is out of range for type 'void *[3]'

Right after the reboot, the AMD GPU briefly failed to detect any connected displays:

amdgpu 0000:c4:00.0: [drm] Cannot find any crtc or sizes

→ This explains the black screen during boot.

Additionally, the following error appears on every boot:

Failed to start systemd-remount-fs.service
/usr/bin/mount for / exited with exit status 32.

→ I believe this is a known harmless issue on Silverblue due to the composefs/read-only root design. Can anyone confirm?

What I have already checked:

  • btrfs device stats /sysroot → all values 0, no filesystem errors
  • dmesg → no NVMe or I/O errors found

Questions:

  1. Is the MT7921 UBSAN bug (mt7921/mcu.c:471) fixed in a newer kernel? Any known workarounds (e.g. module parameters, blacklisting)?
  2. Can the systemd-remount-fs exit-32 error be safely ignored on Fedora Silverblue with composefs?
  3. Are there known issues with AMD GPU display detection after resume (Cannot find any crtc or sizes) on recent Fedora kernels?

Thanks in advance!