# DF-1911 Verification

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

The cited defect exists in the audited source at `sys/dev/drm/radeon/r600_hdmi.c:114-137`. Reproduction
on the running guest is **not possible** because the affected code path is
gated behind hardware that is not present in the audit QEMU/KVM guest
(no AMD/i915 GPU, no LSI MegaRAID, no MMC/SDHCI controller, no FireWire, no
ATAPI floppy, etc.) and/or lives in a kernel module that is not loaded on the
GENERIC-running guest.

## Mechanism (source-only confirmation)
radeon (loaded as module, no radeon HW in guest). Source: r600_audio_update_hdmi at L114-138 walks dev->mode_config.encoder_list with list_for_each_entry but does NOT hold mode_config.mutex. It is scheduled via schedule_work(&rdev->audio_work) from IH ISR (r600.c:4341, evergreen.c:4900, rs600.c:821). Concurrent modeset del can free an encoder mid-walk → UAF.

## Recommended fix
Wrap the encoder_list walk with mutex_lock/unlock(&dev->mode_config.mutex).

The full `git apply`-able diff lives in `fix.diff` in this folder; it was
applied as part of a single combined 41-finding kernel build that compiled
cleanly (rc=0, -Werror clean) — see `../fix_build_summary.txt`.

## Build validation
* `git apply --check` on this fix.diff: **OK**
* Combined kernel build (`X86_64_GENERIC`, INVARIANTS ON) with all 41
  findings' fix.diffs applied: **rc=0**, no warnings, no errors.
* The patched kernel was not booted/run because the affected code path
  requires hardware that the audit guest does not have.