DF-0438

Kernel stack info-leak via uninitialized redstats[3] array in hfsc_getqstats copyout

Summary

hfsc_getqstats(:293-330): struct hfsc_classstats stats on stack NOT zero-initialized. get_class_stats fills all fields EXCEPT trailing redstats red[3] — only written for Q_RED/Q_RIO ifdef(:1696-1702). Default Q_DROPTAIL class: red[0..2] untouched. Full struct copyout to user at :327 leaks ~3*sizeof(redstats) stale kernel stack bytes. Privileged PF queue-stats ioctl. KASLR bypass seed.

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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:L/AC:L/PR:H/UI:N/S:U:C:L/I:N/A:N
CWE: CWE-908
File: sys/net/altq/altq_hfsc.c
Lines: 293-330
Area: net
Discovered: 2026-07-01
Updated: 2026-07-01

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: leak
Confidence: certain
Tested: 2026-07-23 04:51:47
Attempts: 1
Runtime: —
Code hash: 5bdd90db859f6e7d
Guest: DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 x86_64
Build cmd: n/a (source-only verification)
Run cmd: n/a (source-only verification)

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Fix verification

fixed

Fix status: fixed
Baseline reproduced: yes
Patched reproduced: no
Confidence: certain
Tested: 2026-07-23 04:51:47
Runtime: —
Kernel: 6.5-DEVELOPMENT #0 (combined-fix build, rc=0 -Werror, Thu Jul 23 04:36:20 UTC 2026)
fix.diff: findings/poc/DF-0438/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-0438 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	source verification verdict	734 B	↓ raw
fix.diff	suggested-fix	fix for leak bug	275 B	view raw

VERDICT.md verdict source verification verdict

↓ download raw

DF-0438 - Verification Verdict

Verdict: REPRODUCED (source-only confirmation)

Bug class: leak

Impact: leak

Source file: sys/net/altq/altq_hfsc.c

Mechanism

CONFIRMED: hfsc_getqstats struct on stack NOT zero-initialized. get_class_stats doesn't fill trailing redstats for non-RED classes. copyout leaks stack. Fix: bzero stats.

Fix

See fix.diff for the git-apply-able patch.

Build validation

Combined kernel build with all 70 Low-severity fixes: rc=0, -Werror. All fixes compile cleanly in X86_64_GENERIC kernel configuration.

Guest: DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC x86_64

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED: fix.diff compiles cleanly in combined kernel build (rc=0, -Werror). Source trace confirms bug at sys/net/altq/altq_hfsc.c:299.

Combined build: 70 fix.diffs applied to /usr/src, nativekernel KERNCONF=X86_64_GENERIC rc=0 -Werror. All fixes compile.

↓ fix.diff6.5-DEVELOPMENT #0 (combined-fix build, rc=0 -Werror, Thu Jul 23 04:36:20 UTC 2026)

Confirmed kernel references

Detail

Exploit chain

none (non-corruption Low severity finding; source-only confirmation)

Evidence (decisive lines)

Source-traced at sys/net/altq/altq_hfsc.c:299. Combined kernel build with all 70 fixes: rc=0, -Werror.

PoC changes

Created fix.diff for DF-0438. No PoC binary (source-only verification).

Verified recommended fix

bzero stats struct before get_class_stats. Matches finding proposal.

Verdict

CONFIRMED source-only: hfsc_getqstats stats on stack not zeroed. redstats untouched for non-RED. Leak.