# DF-1974 Verification

## Verdict
**SOURCE-CONFIRMED, INCONCLUSIVE-RUNTIME (HW/module gated).**

The cited defect exists in the audited source at `sys/dev/drm/radeon/radeon_encoders.c:368-376`.
radeon is not in GENERIC and requires real radeon GPU hardware.

## Mechanism (source-only confirmation)
radeon_dig_monitor_is_duallink (368-376) does two connector lookups
(active-device then devices-mask); if both return NULL it falls through to
to_radeon_connector(NULL) (container_of with NULL → small negative unmapped
addr) then derefs connector->connector_type. Reachable during modeset before
active_device is set, after MST hot-unplug, or with crafted VBIOS. Called
from 20+ sites in atombios_encoders.c.

## Recommended fix
Add if (!connector) return false; immediately after the fallback lookup,
before to_radeon_connector.

The full `git apply`-able diff lives in `fix.diff` in this folder.