Public bug reported:
############ Summary ############
Running modern Windows games through Steam Proton (DXVK/vkd3d) on Ubuntu
24.04–based Linux Mint consistently triggers kernel oopses in:
syscall_exit_to_user_mode (NULL pointer dereference)
fpregs_assert_state_consistent (FPU state inconsistency)
and previously, on a mainline kernel, amdgpu_hmm_range_get_pages (bad
page map)
These occur across multiple games, not tied to a specific title, and
only under Proton workloads. Hardware stress tests show no instability,
suggesting a kernel regression. The same hardware with a separate
harddrive running windows, has no issues.
############ System Information ############
Distro: Linux Mint 22.x (Ubuntu 24.04 base)
Kernel (affected): 6.14.0-37-generic #37~24.04.1-Ubuntu
Also tested: 6.18.1-061801-generic (mainline, not Ubuntu-supported),
6.6.0-060600, 6.7.0-060700, 6.8.0-90
Motherboard: Gigabyte Z790 UD AC
BIOS: F14 (09/18/2025)
CPU: [Insert output of lscpu | grep 'Model name']
GPU: AMD Radeon RX 7900 XTX
Driver: in‑kernel amdgpu (no proprietary modules)
Taint flags: G D W after oops (no out‑of‑tree modules)
I can attach full outputs of uname -a, lspci -nn, and lsmod if needed.
############ Description of the Problem ############
When running Proton-based games (DX12/DXVK/vkd3d), the kernel
intermittently logs:
1. NULL pointer dereference in syscall_exit_to_user_mode
Example from Europa Universalis V:
#LOG#
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
Oops: 0000 [#2] PREEMPT SMP NOPTI
CPU: 5 PID: 15370 Comm: Task_P_BN 1 Tainted: G D W
6.14.0-37-generic
RIP: 0010:syscall_exit_to_user_mode+0x74/0x1d0
...
note: Task_P_BN 1 exited with irqs disabled
#ENDLOG#
This same oops occurred earlier with a different Proton thread
(ThreadPoolForeg), same kernel, same RIP offset.
2. FPU state inconsistency warning in DXVK shader worker
#LOG#
WARNING: CPU: 4 PID: 8329 at arch/x86/kernel/fpu/core.c:822
fpregs_assert_state_consistent+0x2d/0x50
Comm: dxvk-shader-n Tainted: G D 6.14.0-37-generic
Call Trace:
arch_exit_to_user_mode_prepare
irqentry_exit_to_user_mode
sysvec_reschedule_ipi
#ENDLOG#
This appears during shader compilation under DXVK.
3. On mainline kernel 6.18.1: amdgpu HMM page map corruption
#LOG#
BUG: Bad page map in process vkd3d_queue
amdgpu_hmm_range_get_pages
amdgpu_ttm_tt_get_user_pages
amdgpu_cs_ioctl
#ENDLOG#
To me this might suggest a second failure mode in GPU memory management
under vkd3d.
############ Workloads That Trigger the Bug ############
Arc Raiders (Unreal Engine 5, DX12 via Proton)
Europa Universalis V (DX11/DX12 via Proton)
Both games trigger oopses within minutes.
And multiple other games, the issue is not game-specific.
############ Steps to Reproduce ############
Boot into kernel 6.14.0-37-generic.
Start dmesg -w in a terminal.
Launch Steam → run a Proton game (Arc Raiders or EU5).
Play or idle for a few minutes.
Observe kernel oopses in syscall_exit_to_user_mode or FPU warnings.
Repro rate: high (multiple times per session).
############ Hardware Stability Verification ############
To rule out hardware faults:
I tested on windows which was installed on a separate drive completely, and had
no issues playing games or running benchmarks and no pixel artifact
I ran memtester (4 GB locked, multiple loops)
All tests passed (stuck address, random value, bit fade, etc.)
and ran stress-ng (30 minutes)
Command:
Code
stress-ng --cpu 8 --matrix 4 --vecmath 4 --timeout 30m --metrics-brief
Heavy CPU/FPU/AVX/SIMD load
No errors, kernel warnings and no thermal throttling or instability in
dmesg.
To me this suggests the kernel oopses are not hardware-related.
############ Expected Behavior ############
Proton games should run without triggering kernel oopses in:
syscall exit path
FPU state handling
amdgpu HMM
############ Actual Behavior ############
Kernel logs fatal oopses
Threads exit with IRQs disabled
Kernel becomes tainted
Games may crash or behave unpredictably
System remains running but in an unsafe state, have ran into two kernel
panics, and were not able to grab logs.
############ Additional Notes ############
No proprietary modules loaded
No overclocking; system at stock settings
Issue reproduced across multiple Proton versions
Issue reproduced across multiple games
Issue reproduced across multiple kernels (Ubuntu + mainline)
No errors under synthetic stress tests
############ Conclusion ############
I've been racking my head on this for about a week now on a fresh Mint
install, I wasn't sure where to submit this bug report but thought it
might be a good idea to run it by you guys to see if this is the right
place to report it.
From my (limited) understanding, this appears to be a kernel regression
affecting:
x86 syscall exit path
FPU state tracking
amdgpu HMM under vkd3d
Proton/DXVK workloads on RDNA3 hardware
Given the reproducibility and the clean hardware tests, this seems like
it could be kernal related and not a hardware issue.
I'm happy to try and provide any additiona dmesg/journalctl logging or
proton logs or testing on any other kernels or debug kernels if
needed/requested
Please advise on next steps or additional diagnostics.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2136907
Title:
[REGRESSION?] NULL deref in syscall_exit_to_user_mode and FPU state
warning under Proton/DXVK/vkd3d on Z790 + RX 7900 XTX
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