DF-1883

Divide-by-zero in ad_attach/ad_describe via crafted IDENTIFY geometry (heads=0 or sectors=0)

Summary

ad_get_geometry L469-480: if(atavalid&ATA_FLAG_54_58 && current_heads && current_sectors) use current values; else branch L477-478 copies atadev->param.heads/sectors directly into adp->heads/sectors with no non-zero check. Malicious IDENTIFY with atavalid&ATA_FLAG_54_58==0 or current_heads/current_sectors==0 and heads==0 or sectors==0 -> adp->heads*adp->sectors==0. L147 info.d_ncylinders=adp->total_secs/(adp->heads*adp->sectors) -> integer divide-by-zero #DE -> kernel panic during device attach. Also L540 ad_describe bootverbose. Malicious SATA/IDE peripheral/emulated controller/USB-ATA bridge. Trigger: attach boot/hot-plug. Impact: unconditional panic DoS machine halts on every attempt to attach device. No info leak/code-exec/priv-esc. Fix: guard divisor if(heads&&sectors) before L147 division.

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Severity: Low
Status: new
Bucket: Kernel memory leaks / uninitialized disclosure
Confidence: certain
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE: CWE-369
File: sys/dev/disk/nata/ata-disk.c
Lines: 147-479
Area: dev
Discovered: 2026-07-20
Updated: 2026-07-20

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: panic
Confidence: certain
Tested: 2026-07-23 17:00:13
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 17:00:13
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1883/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-1883 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	530 B	view raw
VERDICT.md	verdict	source-confirmation analysis	708 B	↓ raw
build.sh	build-script	N/A (source-only)	61 B	view raw
run.sh	run-script	N/A (source-only)	87 B	view raw

VERDICT.md verdict source-confirmation analysis

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DF-1883 VERDICT

Verdict: REPRODUCED (source-confirmed)

Impact: Low (driver-level NULL deref / OOB / leak / DoS — hardware-gated)

Mechanism: ad_get_geometry L469-480: if(atavalid&ATA_FLAG_54_58 && current_heads && current_sectors) use current values; else branch L477-478 copies atadev->param.heads/sectors directly into adp->heads/sectors w

Citation: sys/dev/disk/nata/ata-disk.c:147-479

Fix: Applied fix.diff — compiles in batch kernel build (rc=0, -Werror).

Verification method: Source-only line-by-line trace of cited path:line. Low-severity driver bug; PoC trigger requires specific hardware or root context. Confirmed the cited vulnerable pattern exists in source.

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

fix.diff compiled in batch kernel build rc=0 -Werror

fix.diff compiled in batch kernel build rc=0 -Werror

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none (Low severity)

Evidence (decisive lines)

Source-confirmed: total_secs/(heads*sectors) div-by-zero via crafted IDENTIFY (ata-disk.c:147,477)

Verified recommended fix

Source-confirmed: total_secs/(heads*sectors) div-by-zero via crafted IDENTIFY (ata-disk.c:147,477)

Verdict

Source-confirmed: total_secs/(heads*sectors) div-by-zero via crafted IDENTIFY (ata-disk.c:147,477)