# DF-1730 — 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/radeon/atombios_dp.c:312-313`.

## Mechanism
radeon_dp_get_dp_link_config uses max_lane_num from drm_dp_max_lane_count (dpcd&0x1f, up to 31) without clamping to DP-spec max 4; lane_num=8/16 indexes train_set[4] and link_status[6] OOB.

## Fix
Clamp max_lane_num to 4.

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.