DF-4950

ahci_os_stop_port(): unbounded thread-join with no escape converts any port-thread wedge into a permanent unkillable kernel hang at detach/shutdown, and tears down only 1 of the 3 per-port locks

Summary

while(ap_thread) with no timeout - a wedged port thread (DF-3773 class) turns kldunload/detach/reboot into a permanent kernel hang; ap_sim_lock/ap_sig_lock leak per cycle. Bounded-join + uninit-all fix.

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Severity: Low
Status: new
Bucket: Base system — drivers
Confidence: likely
Pass: 2 · GLM 5.3 second pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
CWE: CWE-835
File: sys/dev/disk/ahci/ahci_dragonfly.c
Lines: 248-298
Area: dev
Discovered: 2026-09-25
Updated: 2026-09-25

Team triage

untriaged

priority: — · owner: —

PoC verification

untested

Status: untested
Reproduced: no
Impact: dos
Confidence: likely
Tested: 2026-09-25 08:57:18
Attempts: 0
Runtime: —
Code hash: —
Guest: —
Build cmd: —
Run cmd: —

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Fix verification

not_testable

Fix status: not_testable
Baseline reproduced: —
Patched reproduced: —
Confidence: likely
Tested: 2026-09-25 08:57:18
Runtime: —
Kernel: per-fix-DF-4950
fix.diff: findings/poc/DF-4950/fix.diff
Runner: df-bsd-reviewer

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PoC verification

Evidence pack

findings/poc/DF-4950 · 1 files

File	Type	Description	Size
verdict.json	file		952 B	view raw

Fix verification

not_testable

per-fix-DF-4950

Confirmed kernel references

Detail

Exploit chain

wedged port thread -> detach/shutdown -> infinite while(ap_thread) join -> permanent shutdown hang

Evidence (decisive lines)

findings/poc/DF-4950/ (this verdict)

Verdict

Low (wedge precondition = DF-3773 class + root detach/reboot): ahci_os_stop_port waits for the port thread with NO timeout - a wedged thread (port-lock deadlock, dead hw) turns kldunload/detach/shutdown into a permanent unkillable kernel hang; additionally only 1 of the 3 per-port locks (ap_lock) is ever lockuninit'ed (ap_sim_lock/ap_sig_lock leak per attach/detach cycle). Bounded-join-returning-EBUSY + uninit-all-three fix.