{
  "finding_id": "DF-3253",
  "verdict": "reproduced",
  "impact": "dos",
  "confidence": "certain",
  "reproduce": {
    "build": "cd findings/poc/DF-3253 && ./build.sh",
    "run": "cd findings/poc/DF-3253 && REPS=1 NTHR=8 ITERS=120 ./run.sh badmagic",
    "expected": "baseline: 'DF-3253 SUMMARY: wins=N ebadf(poisoned handoffs seen by stat)=N' + 'UTIMES WIN ... utimes()=0 on a fnode the kernel ALWAYS rejects'; kernel console 'DF3253H: *** INVAL HANDOFF #N ***'; umount panics 'unmount: dangling vnode' intermittently (2/4 runs). With fix.diff applied: wins=0 ebadf=0 einval=960/960, UMOUNT_OK."
  },
  "kernel_refs": [
    "sys/vfs/hpfs/hpfs_hash.c:104",
    "sys/vfs/hpfs/hpfs_hash.c:116",
    "sys/vfs/hpfs/hpfs_hash.c:122",
    "sys/vfs/hpfs/hpfs_hash.c:135",
    "sys/vfs/hpfs/hpfs_vfsops.c:488",
    "sys/vfs/hpfs/hpfs_vfsops.c:506",
    "sys/vfs/hpfs/hpfs_vfsops.c:525",
    "sys/vfs/hpfs/hpfs_vfsops.c:529",
    "sys/vfs/hpfs/hpfs_vfsops.c:538",
    "sys/vfs/hpfs/hpfs_vnops.c:463",
    "sys/vfs/hpfs/hpfs_vnops.c:530",
    "sys/vfs/hpfs/hpfs_vnops.c:1056",
    "sys/kern/vfs_lock.c:589",
    "sys/kern/vfs_vnops.c:894"
  ],
  "artifacts": [
    "README.md", "VERDICT.md", "poc.c", "craft_df3253.py", "build.sh", "run.sh",
    "fix.diff", "instrument_applied.diff", "stats_applied.diff", "instrument_df3253.diff",
    "run.baseline3.badmagic.log", "run.unhashonly.badmagic.log",
    "panic.console.txt", "panic.txt", "panic2.console.txt", "panic2.txt", "panic3.console.txt",
    "env.txt", "verdict.json", "manifest.json"
  ],
  "notes": "Race shape: namei's per-directory vnode lock serializes same-directory lookups (measured 1451 publishes / 0 waiter hits); the handoff needs two dirents in two directories pointing at the same fnode — provided by the crafted image. stat() observes the handoff as EBADF (VNON reaches cvn_stat's type switch, sys/kern/vfs_vnops.c:894); utimes() on the handed-off vnode is a full syscall success (hpfs_setattr has no v_type check). Unmount-after-racing panics 'unmount: dangling vnode' in 2/4 baseline runs. Fix attribution: creator-side hpfs_hphashrem on both post-publish error paths is load-bearing (validated alone: 0 handoffs); hash-side H_INVAL retry is defense-in-depth."
}