⬢ DragonFlyBSD Kernel Audit
DF-3635 / verdict.json
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{
  "finding_id": "DF-3635",
  "status": "untested",
  "reproduced": 0,
  "impact": "none",
  "confidence": "certain",
  "verdict": "Source-certain error-path lock leak, not runtime-testable here. i915_gem_object_get_pages_phys() takes VM_OBJECT_LOCK(vm_obj) at i915_gem.c:305 and jumps to err_phys at :317 on shmem_read_mapping_page() failure without the matching unlock (only the success path at :328 unlocks; err_phys at :357-360 returns directly). VM_OBJECT_LOCK is vm_object_hold() (hold_count ref + LWKT token), so the leak permanently pins the GEM backing vm_object and corrupts token accounting. Reachability is narrow: attach_phys is only invoked from the display modesetting path (intel_display.c:13183) and the failure needs a swap-pager I/O error on a paged-out GEM page (fresh OBJT_DEFAULT pages are zero-filled and cannot fail, sys/vm/default_pager.c:138). Impact ceiling: permanent object leak / VM-accounting wedge (local DoS), no memory-safety primitive. Sibling function i915_gem_object_get_pages_gtt() demonstrates the correct error-path unlock at i915_gem.c:3031-3033, proving the omission is accidental.",
  "exploit_chain": "",
  "evidence": "VERDICT.md control-flow trace; fix.diff adds the missing VM_OBJECT_UNLOCK before goto err_phys, matching the sibling pattern at i915_gem.c:3031-3033.",
  "kernel_refs": [
    "sys/dev/drm/i915/i915_gem.c:305",
    "sys/dev/drm/i915/i915_gem.c:315",
    "sys/dev/drm/i915/i915_gem.c:328",
    "sys/dev/drm/i915/i915_gem.c:357",
    "sys/dev/drm/i915/i915_gem.c:3031",
    "sys/vm/vm_object.c:283"
  ],
  "poc_changes": "No runnable PoC possible (no i915 device on the audit guest; trigger requires Intel hw + display modeset + swap I/O failure). Evidence is source-level.",
  "attempts": 0,
  "guest_uname": "DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026 root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC x86_64",
  "runtime_sec": 0,
  "guest_dirty": 0,
  "build_cmd": "",
  "run_cmd": "",
  "code_hash": "",
  "notes": "Low severity per rubric (requires privileged-adjacent path + pathological storage failure). Recommended fix is the one-line unlock in fix.diff.",
  "recommended_fix": "Add VM_OBJECT_UNLOCK(vm_obj) before goto err_phys in i915_gem_object_get_pages_phys (mirror of i915_gem.c:3031-3033).",
  "fix_status": "not_testable",
  "fix_baseline_reproduced": 0,
  "fix_patched_reproduced": 0,
  "fix_verdict": "One-line symmetric correction matching the sibling get_pages_gtt error path; cannot be kernel-validated on this guest (no i915 device).",
  "fix_evidence": "fix.diff; sibling pattern i915_gem.c:3031-3033."
}