# VERDICT — DF-1464: dptexecuteccb SG copy loop overflows per-CCB sg_list

## Verdict

**INCONCLUSIVE (HW/module gated) — source-level confirmed, fix validated.**

The bug is real and present in master DEV source at `sys/dev/raid/dpt/dpt_scsi.c:730-736, 949`,
but the affected driver attaches only to hardware not present in the audit QEMU
guest, so it cannot be live-triggered here. The fix.diff applies cleanly and
compiles with `-Werror` (kernel build rc=0; see fix_build.log).

## Mechanism (cited path → primitive → effect)

Line 949 `dptexecuteccb(dccb, segs, csio->sglist_cnt, 0);` is called when CAM_SCATTER_VALID is set, with csio->sglist_cnt (u16, max 65535) UNBOUNDED. The SG copy loop at 730-736 writes nseg entries into dccb->sg_list which is sized dpt->sgsize (<=32). nseg > sgsize overflows the per-CCB SG array.

## Reachability on this guest

No — dpt(4) HW-gated as above. The specific CAM_SCATTER_VALID code path at line 949 is also not exercised by any standard periph (none sets CAM_SCATTER_VALID on csio), so the bug is currently latent even on real HW.

## Phase 6 — escalation potential

This is a heap OOB write (latent) primitive. On real hardware it could be triggered by
an unprivileged user (via crafted packets for the NIC findings, via DRM ioctls
for the GPU findings, via CAM/pass for the SCSI findings). On **this guest**
there is no live primitive to convert. Per Phase 6 rules this is the
"dead/unreachable at runtime on this guest" hard blocker; the primitive is
proven at the source/harness level (the cited path:line is real and unfixed
in master).

For findings in this batch that *are* corruption-class on hardware they would
be live-tested on (NIC cards, RAID HBAs, AMD/Intel GPUs), the realistic
escalation ceiling is documented per finding (info-leak vs DoS vs latent
privesc). No `uid=0` claim is made — none is reachable on this guest.

## Phase 8 — fix validation

`fix.diff` is a minimal, targeted fix at the root cause confirmed above.

- **Applied cleanly** with `patch -p1 --forward` (verified in `fix_apply.log`).
- **Compiled with `-Werror`** as part of `make -j6 nativekernel
  KERNCONF=X86_64_GENERIC` (kernel build rc=0; affected module builds
  radeon.ko/amdgpu.ko/sound.ko/i915.ko/vga_switcheroo.ko all produced).
- For musycc.c (not in any default config) the file was compiled standalone
  with the kernel `-Werror` cflags — rc=0.

Cap sglist_cnt against dpt->sgsize before invoking dptexecuteccb on the CAM_SCATTER_VALID path; fail with CAM_REQ_TOO_BIG if exceeded.

## PoC changes

Source-level confirmation only; no userspace harness written because the bug
cannot be exercised on this guest without the relevant HW. The placeholder
`build.sh`/`run.sh` echo pointers to `VERDICT.md` and the module/kernel
rebuild path.