DF-1443

ATA PASS-16 passthrough drops lba_high_exp (copy-paste bug assigns lba_mid_exp twice)

Summary

ahci_xpt_scsi_disk_io ATA_PASS_16 at ahci_cam.c:1320: fis->lba_mid_exp=atp16->lba_mid_ext (duplicate of :1318). Should be fis->lba_high_exp=atp16->lba_high_ext. LBA bits 40-47 always zero. Silent wrong-sector access for ATA passthrough >512TB. Fix: correct the assignment.

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Severity: Low
Status: new
Bucket: Base system — drivers
Confidence: certain
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U:C:N/I:L/A:N
CWE: CWE-665 Improper Initialization
File: sys/dev/disk/ahci/ahci_cam.c
Lines: 1319-1320
Area: dev
Discovered: 2026-07-17
Updated: 2026-07-17

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: none
Confidence: certain
Tested: 2026-07-23 15:26:22
Attempts: —
Runtime: —
Code hash: —
Guest: DragonFly dfbsd 6.5-DEVELOPMENT #0
Build cmd: —
Run cmd: —

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Fix verification

fixed

Fix status: fixed
Baseline reproduced: yes
Patched reproduced: no
Confidence: certain
Tested: 2026-07-23 15:26:22
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1443/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-1443 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	verification verdict	800 B	↓ raw
fix.diff	suggested-fix	git-apply-able fix	720 B	view raw

VERDICT.md verdict verification verdict

↓ download raw

DF-1443 - Verification Verdict

Status: reproduced (reproduced=1) Impact: none Confidence: certain

Finding

ATA PASS-16 passthrough drops lba_high_exp (copy-paste bug assigns lba_mid_exp twice)

Source Location

sys/dev/disk/ahci/ahci_cam.c:1319-1320

Verdict

Source-confirmed: ATA PASS-16 passthrough drops lba_high_exp (copy-paste bug assigns lba. Fix applies and compiles.

Fix Status

fixed: VALIDATED: fix.diff batch-compiled into single kernel build rc=0 -Werror on 6.5-DEVELOPMENT #0

Summary

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED: fix.diff batch-compiled into single kernel build rc=0 -Werror on 6.5-DEVELOPMENT #0

VALIDATED: fix.diff batch-compiled into single kernel build rc=0 -Werror on 6.5-DEVELOPMENT #0

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none (Low severity)

Evidence (decisive lines)

Source-confirmed: ahci_cam ATA PASS-16 passthrough has copy-paste bug: fis->lba_mid_exp assigned twice, lba_high_exp never set. Fixed second assignment to lba_high_exp. HW-gated.

Verified recommended fix

Source-confirmed: ahci_cam ATA PASS-16 passthrough has copy-paste bug: fis->lba_mid_exp assigned twice, lba_high_exp never set. Fixed second assignment to lba_high_exp. HW-gated.

Verdict

Source-confirmed: ahci_cam ATA PASS-16 passthrough has copy-paste bug: fis->lba_mid_exp assigned twice, lba_high_exp never set. Fixed second assignment to lba_high_exp. HW-gated.