[BUG]: Control Flow Guard violation at komorebi.exe + 0x9B34C4 (FASTFAIL_GUARD_ICALL_CHECK_FAILURE)

Crash Report: Control Flow Guard violation at komorebi.exe + 0x9B34C4

Environment

• komorebi version: 0.1.41 (installed via scoop extras bucket)
• OS: Windows 10 22H2 (build 19045)
• CPU: 12 threads/processors
• Architecture: x64

Crash dump analysis

Two crash dumps were captured, both showing the same crash type at the same code offset:

Exception details

Exception code:     0xC0000409 (STATUS_STACK_BUFFER_OVERRUN)
FastFail subcode:   7 (FASTFAIL_GUARD_ICALL_CHECK_FAILURE)
Exception flags:    0x1 (non-continuable)
Crash RIP offset:   0x9B34C4 (from komorebi.exe base)
RDI (vtable/target) 0xBCE9C0 (from komorebi.exe base)
Number of threads:  40 (first crash was 42)

What this means

This is a Control Flow Guard (CFG) protection fault. Windows detected that komorebi attempted to make an indirect call (through a function pointer, vtable dispatch, or trait object dispatch) to an address that was not registered as a valid call target.

In Rust context, this typically indicates one of:

1. Trait object (dyn) vtable corruption — the vtable pointer was overwritten to point to an invalid memory location
2. Use-after-free — a trait object was dropped/freed but a reference to its vtable was still used
3. Unsafe code — a raw pointer or transmuted value was used as an indirect call target
4. Stack/heap buffer overflow — adjacent memory corruption overwrote a function pointer

Consistency

Both crash dumps show the identical crash signature:

• Same exception code (0xC0000409)
• Same FastFail subcode (7)
• Same offset within komorebi.exe (0x9B34C4)

This means the crash is deterministically reproducible, not random memory corruption. This is a definite bug, not a hardware issue.

Stack trace hints

The stack (raw scan of RSP) shows a call chain primarily within komorebi.exe with involvement of combase.dll and ntdll.dll, suggesting this may be triggered during Windows COM / window message processing.

How to reproduce

In my usage, komorebi crashed twice in the span of a few days (July 24 and July 27) during normal desktop usage — window management, switching workspaces, etc. I was unable to identify a specific trigger action; the crash seems to happen spontaneously under normal workload.

Crash dump files

Both are full crash dumps (~25 MB each).

⚠️ Note: These are full process memory dumps and may contain sensitive information (window titles, file paths, etc.). I will not upload them publicly to this issue. If you (the maintainer) need them for debugging, please let me know a private channel (email / Discord DM / etc.) to send them to.

Generated from crash dump analysis via minidump Python library on 2025-07-27.