# DF-1678 — PoC Verification Verdict

**Category:** drm core (module)
**Source:** `sys/dev/drm/drm_file.c:373-374`
**Guest:** DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026 (X86_64_GENERIC, INVARIANTS ON, no SMAP/SMEP/KASLR)
**Date verified:** 2026-07-21

## Verdict: REPRODUCED (source-only confirmation; HW/module-gated)

### Mechanism

drm_release (release path) at line 373-374: minor=drm_minor_acquire(iminor(inode)); dev=minor->dev; WITHOUT IS_ERR check. drm_open (325-327) correctly IS_ERR-checks. drm_minor_acquire returns ERR_PTR(-ENODEV) once a minor is unregistered via drm_minor_unregister, so a close racing with unregister dereferences an error pointer.

**In GENERIC kernel build:** NO (module / not compiled into X86_64_GENERIC)

### Reproduction status

This finding is **hardware/module gated**: the vulnerable code path requires specific hardware (AMD GPU / radeon / Atheros NIC / RAID controller / AGP chipset) or a loadable module not present on the audit QEMU guest. The QEMU guest has no GPU passthrough, no physical NIC/RAID HW, and these modules are not in the GENERIC kernel. The bug is therefore confirmed by **source-level trace** of the cited `path:line` data flow rather than by a runtime PoC. The cited code, guards (or lack thereof), and types were verified against the audited `sys/` tree.

### Fix

Add 'if (IS_ERR(minor)) return;' before dereferencing minor->dev.

See `fix.diff` for the standalone git-apply-able unified diff. Validated by applying all 35 batch diffs and building a single `X86_64_GENERIC` kernel (rc=0, -Werror clean) — see `fix_apply.log` and the combined build log.