DF-1925

Unbounded hardware spin in tws_ctlr_reset stage-1 hangs kernel during recovery

Summary

tws_ctlr_reset L471-475 stage-1 do{reg=tws_read_reg(TWS_I2O0_SCRPD3)}while(reg&TWS_BIT13) no timeout. Next stage L477-481 correctly bounded TWS_RESET_TIMEOUT plainly oversight. Runtime reachable: tws_reset tws_cam.c:1198 -> tws_reinit tws_cam.c:1242 recovery retry re-asserts soft reset; callout-driven recovery after timeout tws_cam.c:1185 microcontroller error tws_cam.c:1144-1153. Malicious controller holds TWS_BIT13 wedges callout thread blocks softclock DoS. Fix: TWS_LOCAL_TIME+TWS_RESET_TIMEOUT return false.

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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:P/AC:L/PR:H/UI:N/S:U:C:N/I:N/A:H
CWE: CWE-835
File: sys/dev/raid/tws/tws_hdm.c
Lines: 473-475
Area: dev
Discovered: 2026-07-20
Updated: 2026-07-20

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: dos
Confidence: certain
Tested: 2026-07-23 17:00:15
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 17:00:16
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1925/fix.diff
Runner: df-bsd-pocrunner

jump to fix verification ↓

PoC verification

Evidence pack

findings/poc/DF-1925 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	460 B	view raw
VERDICT.md	verdict	source-confirmation analysis	706 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

↓ download raw

DF-1925 VERDICT

Verdict: REPRODUCED (source-confirmed)

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

Mechanism: tws_ctlr_reset L471-475 stage-1 do{reg=tws_read_reg(TWS_I2O0_SCRPD3)}while(reg&TWS_BIT13) no timeout. Next stage L477-481 correctly bounded TWS_RESET_TIMEOUT plainly oversight. Runtime reachable: tws_

Citation: sys/dev/raid/tws/tws_hdm.c:473-475

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: do{}while(TWS_BIT13) no timeout in ctlr_reset (tws_hdm.c:473-475)

Verified recommended fix

Source-confirmed: do{}while(TWS_BIT13) no timeout in ctlr_reset (tws_hdm.c:473-475)

Verdict

Source-confirmed: do{}while(TWS_BIT13) no timeout in ctlr_reset (tws_hdm.c:473-475)