# DF-2317 — PoC verdict

**File:** `sys/bus/mmc/mmc.c`

**Verdict:** NOT REPRODUCED on this QEMU guest — confirmed HW/ACPI/device-gated; the code bug is REAL and a defense-in-depth `fix.diff` is attached.

## Mechanism (confirmed in source)

mmc_decode_csd_sd() extracts the 2-bit CSD structure version from raw card data and panics ("unknown SD CSD version") for any value other than 0 or 1. The card fully controls those bits (CMD9 CSD response).

### Cited lines

- `sys/bus/mmc/mmc.c:1056`
- `sys/bus/mmc/mmc.c:1108-1109`

## Why it does not reproduce on this guest

No mmc/sd controller or card on the QEMU guest (no /dev/mmcsd*, mmc module not loaded, devinfo shows no mmc bus).

Guest gate-proof (full `usbconfig`/`pciconf`/`ifconfig`/`devinfo`/`sysctl`/`kldstat` output) is in `env.txt`.

## Defense-in-depth fix

Replace panic() with a kprintf log and leave csd zeroed so the caller rejects the card instead of crashing the kernel.

The git-apply-able diff is in `fix.diff` (verified `git apply --check` clean).

## Classification

- `status`: not_reproduced
- `reproduced`: 0
- `impact`: none (not reachable on this guest; latent code bug confirmed in source)
- `confidence`: certain (code bug + gate both confirmed by direct source trace and guest enumeration)
- `fix_status`: not_testable (patch applies + compiles-correct by inspection, but no live device to exercise on this guest)