# DF-1807 — Verdict

**Severity:** Low
**Status:** REPRODUCED (source-only confirmation — driver/HW-gated, not runtime-triggered on QEMU guest)
**Impact:** panic
**Confidence:** certain

## Verdict
REPRODUCED. The cited bug is confirmed real in the audited source at `sys/dev/drm/amd/amdgpu/amdgpu_fence.c:424,435`.

## Mechanism
amdgpu_fence_driver_init_ring power-of-two check (n&(n-1)) accepts 0; num_hw_submission=0 yields num_fences_mask=UINT_MAX, kcalloc(0)=ZERO_LENGTH_PTR non-NULL, first fence emit derefs NULL.

## Fix
Add !num_hw_submission to the validation check.

The full git-apply-able diff is in `fix.diff`.

## Build validation
fix.diff applies cleanly and compiles with `-Werror` as part of the batch module build
(all 51 fixes applied to /usr/src, kernel+modules built).

## Notes
Source-only confirmation: this finding is in a GPU/display code path that requires
specific hardware not present in the QEMU guest. The bug is confirmed by source tracing
(cited path:line verified against sys/), and the fix compiles clean. No runtime trigger
was attempted as the relevant device/module is HW-gated.