# DF-1940 Verification

## Verdict
**SOURCE-CONFIRMED, INCONCLUSIVE-RUNTIME (HW/module gated).**

The cited defect exists in the audited source at `sys/dev/disk/nata/chipsets/ata-intel.c:471-478`. Reproduction
on the running guest is **not possible** because the affected code path is
gated behind hardware that is not present in the audit QEMU/KVM guest
(no AMD/i915 GPU, no LSI MegaRAID, no MMC/SDHCI controller, no FireWire, no
ATAPI floppy, etc.) and/or lives in a kernel module that is not loaded on the
GENERIC-running guest.

## Mechanism (source-only confirmation)
nata IS in GENERIC. Source: ata_intel_31244_tf_write at L471-478 (when ATA_D_USE_CHS set): lba%sectors, lba/(sectors*heads), sectors*heads — no zero check on heads/sectors. heads/sectors from atadev->param.current_heads/current_sectors (when atavalid&ATA_FLAG_54_58) or param.heads/sectors. A crafted IDENTIFY with heads=0 or sectors=0 divides by zero.

## Recommended fix
Add `if (heads == 0 || sectors == 0) return;` before the LBA math.

The full `git apply`-able diff lives in `fix.diff` in this folder; it was
applied as part of a single combined 41-finding kernel build that compiled
cleanly (rc=0, -Werror clean) — see `../fix_build_summary.txt`.

## Build validation
* `git apply --check` on this fix.diff: **OK**
* Combined kernel build (`X86_64_GENERIC`, INVARIANTS ON) with all 41
  findings' fix.diffs applied: **rc=0**, no warnings, no errors.
* The patched kernel was not booted/run because the affected code path
  requires hardware that the audit guest does not have.