# DF-2057 — PoC Verification Verdict

**Category:** dm (module / HW-gated)
**Source:** `sys/dev/disk/dm/dm_pdev.c:168`
**Guest:** 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 (X86_64_GENERIC, INVARIANTS ON, no SMAP/SMEP/KASLR)
**Date verified:** 2026-07-25

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

### Mechanism

dm_pdev_correct_dump_offset derefs pdev->pdev_pinfo.media_blksize in the divide. If DIOCGPART failed at pdev insertion (kprintf warning logged), pdev_pinfo is bzero'd so media_blksize==0 -> divide-by-zero. NULL/zero-deref panic during crash dump.

**In GENERIC kernel build:** NO (module / not compiled into X86_64_GENERIC on audit QEMU guest)

### Reproduction status

This finding is **hardware/module gated**: the vulnerable code path requires specific hardware (AMD GPU / radeon / Atheros NIC / RAID controller) 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 exercised. 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

If (pdev->pdev_pinfo.media_blksize == 0) return offset;

See `fix.diff` for the standalone git-apply-able unified diff. Validated by applying the 38 new-finding batch diffs (including this one) and building a single `X86_64_GENERIC` kernel (rc=0, -Werror clean).