{
 "finding_id": "DF-2876",
 "status": "reproduced",
 "reproduced": 1,
 "impact": "leak",
 "confidence": "certain",
 "verdict": "diskiodone attaches bp->b_data/b_bcount to the BLK reply before checking B_ERROR/b_resid (subr_diskiocom.c:594-597, :651-655), so a read that transfers nothing ships the stale contents of the SHARED getpbuf_mem KVA arena (vm_pager.c:505 - reused by every process's raw-device physio, kern_physio.c:43, and disk label probes). Verified: a BLK_READ at exact EOF on a vnode-backed vn disk (VOP_READ returns success with untouched resid) returned error=0 resid=65536 with a 64KB aux byte-identical (md5) to a previous root process's physio buffer of a 'secret' image; a second run leaked the BOOT DISK's MBR boot code through a different disk's channel (cross-device). Fixed kernel returns aux=0.",
 "exploit_chain": "dmsg peer -> BLK_READ at/after media EOF (or any erroring read) -> reply aux = most recent raw-I/O buffer of ANY process on the machine (up to MAXPHYS per request, repeatable) -> harvest other tenants'/root's disk traffic (backups, fsck scans, other cluster nodes' data)",
 "evidence": [
  "run.log (error=0 resid=65536 aux=65536; LEAK_RUN_1 FULL_64K_BLOCK_MATCHES_SECRET; run2 leaked boot-sector bytes fc310c8e...)",
  "leak_sample.txt",
  "f3_leak_1.bin == f3_secret.bin (md5 7081aa33857826393038748400c1ee27)",
  "run.fix.log (aux=0 x3 on fix kernel)"
 ],
 "kernel_refs": [
  "sys/kern/subr_diskiocom.c:594",
  "sys/kern/subr_diskiocom.c:600",
  "sys/kern/subr_diskiocom.c:651",
  "sys/kern/subr_diskiocom.c:655",
  "sys/vm/vm_pager.c:505",
  "sys/kern/kern_physio.c:43"
 ],
 "poc_changes": "No seed; wrote dfpeer.c eofread mode; deterministic EOF trigger discovered via vn(4) vnode strategy (success + untouched uio_resid at EOF)",
 "attempts": 2,
 "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": 420,
 "guest_dirty": 1,
 "build_cmd": "cc -O -Wall -o /tmp/dfpeer dfpeer.c",
 "run_cmd": "sh run_f3.sh (root)",
 "code_hash": "e748ca2203c63d4fc7c412513eefcdf465800329f3e8ff3c36dbd9f5d0583722",
 "notes": "Same runs also demonstrate the arena is global across devices (boot-disk MBR via vn0 channel).",
 "recommended_fix": "On B_ERROR attach no data; on short reads attach only completed bytes (b_bcount - b_resid)",
 "fix_status": "fixed",
 "fix_kernel_uname": "DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #1: Wed Sep  2 18:43:16 UTC 2026 root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC x86_64 (fix.diff applied, make nativekernel)",
 "fix_baseline_reproduced": 1,
 "fix_patched_reproduced": 0,
 "fix_verdict": "Fix kernel: all three EOF-read runs return aux=0 (resid still reported). Leak dead.",
 "fix_evidence": [
  "run.fix.log"
 ]
}