# DF-1782 — Verdict

**Severity:** Low
**Status:** REPRODUCED (source-only confirmation — driver/HW-gated, not runtime-triggered on QEMU guest)
**Impact:** none
**Confidence:** certain

## Verdict
REPRODUCED. The cited bug is confirmed real in the audited source at `sys/dev/disk/nata/chipsets/ata-siliconimage.c:410`.

## Mechanism
ata_sii_setmode PIO branch indexes piotimings[mode & ATA_MODE_MASK] where masked index is 8-12 for PIO0-PIO4, reading 3-8 uint16 past the 5-element array; garbage programmed as PIO timing.

## Fix
Subtract ATA_PIO0 from the masked index.

The full git-apply-able diff is in `fix.diff`.

## Build validation
fix.diff applies cleanly and compiles with `-Werror` as part of the batch module build
(all 51 fixes applied to /usr/src, kernel+modules built).

## Notes
Source-only confirmation: this finding is in a device driver code path that requires
specific hardware not present in the QEMU guest. The bug is confirmed by source tracing
(cited path:line verified against sys/), and the fix compiles clean. No runtime trigger
was attempted as the relevant device/module is HW-gated.