DF-1425

Unchecked HBA-controlled msg_len in screen-service writes NUL byte at arbitrary scratch offset

Summary

gdt_sync_event at iir.c:1720-1725: msg_len from HBA DMA gc_scratch[GDT_SCR_MSG_LEN] (u32). gc_scratch[GDT_SCR_MSG_TEXT+msg_len]=0 with no bound vs GDT_SCRATCH_SZ. msg_len>3056 -> NUL write past scratch into adjacent kernel heap. Also kprintf over-reads if text is NUL-free. Malicious/buggy HBA DMA. Fix: clamp msg_len to GDT_SCRATCH_SZ-GDT_SCR_MSG_TEXT-1.

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Severity: Low
Status: new
Bucket: Kernel memory corruption (UAF / OOB write)
Confidence: likely
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U:C:N/I:L/A:H
CWE: CWE-787 Out-of-bounds Write; CWE-129 Improper Validation of Array Index
File: sys/dev/raid/iir/iir.c
Lines: 1717-1725
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: likely
Tested: 2026-07-23 15:26:21
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: likely
Tested: 2026-07-23 15:26:21
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1425/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-1425 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	verification verdict	885 B	↓ raw
fix.diff	suggested-fix	git-apply-able fix	979 B	view raw

VERDICT.md verdict verification verdict

↓ download raw

DF-1425 - Verification Verdict

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

Finding

Unchecked HBA-controlled msg_len in screen-service writes NUL byte at arbitrary scratch offset

Source Location

sys/dev/raid/iir/iir.c:1717-1725

Verdict

Source-confirmed: Unchecked HBA-controlled msg_len in screen-service writes NUL byte at . 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: iir gdt_sync_event writes NUL at gc_scratch[GDT_SCR_MSG_TEXT+msg_len] using unchecked HBA-supplied msg_len. Added imin() bound. HW-gated.

Verified recommended fix

Source-confirmed: iir gdt_sync_event writes NUL at gc_scratch[GDT_SCR_MSG_TEXT+msg_len] using unchecked HBA-supplied msg_len. Added imin() bound. HW-gated.

Verdict

Source-confirmed: iir gdt_sync_event writes NUL at gc_scratch[GDT_SCR_MSG_TEXT+msg_len] using unchecked HBA-supplied msg_len. Added imin() bound. HW-gated.