[kernel 6.5.x and higher] UBSAN AMD driver-errors during boot

[thom]

Hi all,

I'm testdriving Ubuntu-MATE 24.04 at the moment.
The version that is due to come out in april this year.

Kernel 6.6.0 introduced some GPU driver errors

during boot, before Xorg starts, these AMD driver-errors were displayed:

[ 4.810856] ================================================================================
[ 4.810875] UBSAN: array-index-out-of-bounds in /build/linux-xR9R4C/linux-6.6.0/drivers/gpu/drm/radeon/radeon_atombios.c:2717:34
[ 4.810894] index 16 is out of range for type 'UCHAR [1]'
[ 4.814341] ================================================================================
[ 4.814354] UBSAN: array-index-out-of-bounds in /build/linux-xR9R4C/linux-6.6.0/drivers/gpu/drm/radeon/radeon_atombios.c:2705:39
[ 4.814373] index 2 is out of range for type 'ATOM_PPLIB_NONCLOCK_INFO [1]'
[ 4.823056] ================================================================================
[ 4.823090] UBSAN: array-index-out-of-bounds in /build/linux-xR9R4C/linux-6.6.0/drivers/gpu/drm/radeon/radeon_atombios.c:2715:55
[ 4.823144] index 1 is out of range for type 'UCHAR [1]'
[ 4.827017] ================================================================================
[ 4.827035] UBSAN: array-index-out-of-bounds in /build/linux-xR9R4C/linux-6.6.0/drivers/gpu/drm/radeon/sumo_dpm.c:1495:39
[ 4.827056] index 2 is out of range for type 'ATOM_PPLIB_NONCLOCK_INFO [1]'

[thom (tsk)]

The crashing of Xorg had nothing to do with the mentioned booterrors.

I changed the description and the title of this bug accordingly

[thom (tsk)]

I found new info:

First, this errormessage always pop up with all AMD drivers on newer kernels.

https://gitlab.freedesktop.org/drm/amd/-/issues/2874

Most important takeaway from this is the comment of Alex Deucher: "All of these are variable sized arrays so these are false positives."

Although innocent, it may needlessly worry a lot of people that encounter it for the first time.