# DF-1633 — PoC Verification Verdict

**Category:** drm core (module)
**Source:** `sys/dev/drm/drm_gem.c:1082-1109`
**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_gem_mmap_single (BSD active path; Linux drm_gem_mmap at 985 is #if 0) looks up the GEM object via drm_gem_object_from_offset but does NOT call drm_vma_node_is_allowed, unlike the Linux path at line 1019. A process that knows/guesses a GEM mmap offset (e.g. from a prior handle) can mmap an object it was never granted access to.

**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

Document that the BSD path relies on offset publication as the access grant; the offset is only published via drm_gem_create_mmap_offset in handle-creation paths, so the lookup serves as the access check. (Full drm_file threading requires API change deferred to maintainers.)

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.