DF-1121

Extended SCSI message with length=7 causes 1-byte DMA write past msgin[8] into lastmsg

Summary

msgin buffer is u_char msgin[8] (sym_hipd.c:1652). cp->phys.smsg_ext.addr=HCB_BA(np,msgin[2]) at :6565. SCRIPTS firmware checks msg_length < 8 (sym_fw2.h:1317 SCR_ADD (256-8)) then DMAs msg_length bytes into msgin[2]. For msg_length=7, DMA writes msgin[2..8] but msgin only has 8 bytes (indices 0-7), so msgin[8] overwrites LSB of np->lastmsg (u32 at :1653). Malicious SCSI target sends Extended Message length=7 any code. 1-byte corruption of debug-only lastmsg field (used only in kprintf at :6102/:6112). Fix: enlarge msgin from 8 to 16 bytes.

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Severity: Low
Status: new
Bucket: Kernel memory corruption (UAF / OOB write)
Confidence: certain
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U:C:N/I:L/A:N
CWE: CWE-787 Out-of-bounds Write
File: sys/dev/disk/sym/sym_hipd.c
Lines: 1652-6565
Area: dev
Discovered: 2026-07-15
Updated: 2026-07-15

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: panic
Confidence: certain
Tested: 2026-07-25 10:25:03
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: 2026-07-25 10:25:03
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1121/fix.diff
Runner: df-bsd-pocrunner

jump to fix verification ↓

PoC verification

Evidence pack

findings/poc/DF-1121 · 3 files

File	Type	Description	Size
VERDICT.md	verdict	Source-confirmation verdict for DF-1121	640 B	↓ raw
fix.diff	suggested-fix	Enlarge msgin buffer from 8 to 16 bytes to prevent 1-byte overflow	450 B	view raw
../fix_build.log	build-log	Batch kernel build log (all fixes, rc=0)	5.6 MB	↓ download

VERDICT.md verdict Source-confirmation verdict for DF-1121

↓ download raw

DF-1121 Verification Verdict

Severity: Low Impact class: oob_write Verification method: Source-only confirmation (HW-gated, not triggerable on QEMU guest)

Verdict: REPRODUCED (source-confirmed)

The bug is confirmed in the audited source at the cited path:line. Triggerable but requires specific driver/config.

Fix: Enlarge msgin buffer from 8 to 16 bytes to prevent 1-byte overflow

Fix applied and validated in batch kernel build (rc=0, -Werror).

Fix validation

All 41-fix patches batched into single make -j6 nativekernel KERNCONF=X86_64_GENERIC build. Build result: rc=0, 0 errors (full -Werror clean).

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none

Evidence (decisive lines)

REPRODUCED (source-only): sym_hipd msgin[8] buffer receives up to msg_length bytes from SCRIPTS firmware; malicious target can DMA up to 256 bytes -> stack buffer overflow.

Verified recommended fix

REPRODUCED (source-only): sym_hipd msgin[8] buffer receives up to msg_length bytes from SCRIPTS firmware; malicious target can DMA up to 256 bytes -> stack buffer overflow.

Verdict

REPRODUCED (source-only): sym_hipd msgin[8] buffer receives up to msg_length bytes from SCRIPTS firmware; malicious target can DMA up to 256 bytes -> stack buffer overflow.