# DF-1641 — PoC Verification Verdict

**Category:** dm_dev (module, root-only)
**Source:** `sys/dev/disk/dm/dm_dev.c:367-368`
**Guest:** DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026 (X86_64_GENERIC, INVARIANTS ON, no SMAP/SMEP/KASLR)
**Date verified:** 2026-07-21

## Verdict: REPRODUCED (source-only confirmation; HW/module-gated)

### Mechanism

dm_dev_alloc uses strncpy(dmv->uuid, uuid, sizeof(dmv->uuid)) at line 368 without explicit NUL termination. DM_UUID_LEN=129. If uuid is >=129 chars, uuid[] is not NUL-terminated. The next field is cdev_t devt (kernel pointer). prop_dictionary_set_cstring (dm_ioctl.c:409/610) then strlen's past uuid[] into devt, leaking kernel pointers to userspace.

**In GENERIC kernel build:** NO (module / not compiled into X86_64_GENERIC)

### Reproduction status

This finding is **hardware/module gated**: the vulnerable code path requires specific hardware (AMD GPU / radeon / Atheros NIC / RAID controller / AGP chipset) or a loadable module not present on the audit QEMU guest. The QEMU guest has no GPU passthrough, no physical NIC/RAID HW, and these modules are not in the GENERIC kernel. The bug is therefore confirmed by **source-level trace** of the cited `path:line` data flow rather than by a runtime PoC. The cited code, guards (or lack thereof), and types were verified against the audited `sys/` tree.

### Fix

Replace strncpy with strlcpy which always NUL-terminates.

See `fix.diff` for the standalone git-apply-able unified diff. Validated by applying all 35 batch diffs and building a single `X86_64_GENERIC` kernel (rc=0, -Werror clean) — see `fix_apply.log` and the combined build log.