{
  "finding_id": "DF-3057",
  "status": "reproduced",
  "reproduced": 1,
  "impact": "leak",
  "confidence": "certain",
  "verdict": "REPRODUCED (deterministic harness; dirfs vkernel-only, no live-boot test). dirfs_write :740-741 assigns error=bread(...) then immediately overwrites it with error=uiomovebp(...); :752-755 ignore the bwrite()/bdwrite() results. bread always returns a buffer but on a failed strategy (host pread EIO on the backing file / invalid dn_fd / stale dn_size) the block is NOT filled; dirfs_write then overlays the user's bytes, flushes the whole 16KB block via pwrite(dn_fd), and returns success. Harness (real file + read-back): stale bytes of another file appear in the target file at the expected offset (info leak into attacker-readable file, CWE-909) and write() returns 0 despite EIO; IO_SYNC bwrite failures equally invisible. Fixed variant (check bread error; propagate bwrite error) reports EIO and persists nothing.",
  "exploit_chain": "failing backing file (host EIO) + partial-block write through dirfs -> unfilled buffer span persisted to the target file -> attacker reads back stale buffer-cache contents of other files on the mount (cross-file disclosure within the vkernel) + silent data corruption; write()/fsync-adjacent semantics report success. Trigger is narrow (requires the host read to fail) \u2014 rated Medium.",
  "evidence": "harness.c (verbatim loop transcription with bread-fails-without-fill model; getblk-reuse modeled by pre-seeding the buffer with another file's canary); run.log: 'bread failed with EIO but write() returns: 0', 'STALE DATA FROM ANOTHER FILE present at offset 7000', 'INFO LEAK ... CONFIRMED'; FIXED: 'write() returns: 5 (EIO)', 'no stale data => NO LEAK'. Deterministic over 3 runs.",
  "kernel_refs": [
    "sys/vfs/dirfs/dirfs_vnops.c:740",
    "sys/vfs/dirfs/dirfs_vnops.c:741",
    "sys/vfs/dirfs/dirfs_vnops.c:742",
    "sys/vfs/dirfs/dirfs_vnops.c:752",
    "sys/vfs/dirfs/dirfs_vnops.c:753",
    "sys/vfs/dirfs/dirfs_vnops.c:817",
    "sys/vfs/dirfs/dirfs_vnops.c:830",
    "sys/kern/vfs_bio.c:900",
    "sys/kern/vfs_bio.c:960"
  ],
  "poc_changes": "Harness written fresh (no seed). One iteration: replaced memmem() (absent on DF libc) with a portable scan.",
  "attempts": 1,
  "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": 5,
  "guest_dirty": 0,
  "build_cmd": "cd poc/DF-3057 && sh build.sh",
  "run_cmd": "cd poc/DF-3057 && sh run.sh",
  "code_hash": "6ddf6759a4245a3fbe8065232f9a2d99c42e79a4ba816d5a1813679d0c0c35c0",
  "notes": "Extension writes do NOT hit this (pread past EOF returns 0 and dirfs_strategy bzeros the block); the failing-read precondition is a genuine host I/O error or an invalidated dn_fd.",
  "recommended_fix": "dirfs_write: check bread() error before uiomovebp (brelse+break), and propagate the bwrite() return for IO_SYNC writes.",
  "fix_status": "not_testable",
  "fix_kernel_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",
  "fix_baseline_reproduced": 1,
  "fix_patched_reproduced": 1,
  "fix_verdict": "fix.diff applies cleanly (git apply --check RC=0 on the local sys/ tree and on the guest /usr/src). Compile-neutral: patched vs unpatched dirfs_vnops.o/dirfs_subr.o compile attempts in the vkernel64 build env fail with IDENTICAL first errors (pre-existing ad-hoc-env include breakage, same as DF-0806 documented) - fix_*.log in this pack. Behavior validated by the harness FIXED variant (no crash / correct file / EIO propagated). Live boot validation not_testable: dirfs is vkernel-only (sys/platform/vkernel64/conf/files) and is not compiled into the guest host kernel, so the patched code path cannot be exercised by a host-kernel reboot.",
  "fix_evidence": "fix.diff; fix_base_vnops.log vs fix_p3057_vnops.log (identical first error); harness FIXED variant output in run.log"
}