DF-0442

rmc_init stores user-driven maxqueued_ without validation: div-by-zero or heap OOB via fixed-size array modulus

Summary

rmc_init(:680): ifd->maxqueued_=maxqueued no bounds check. Used as modulus qi_=(qi_+1)%maxqueued_(:1086,:1206), qo_=(qo_+1)%maxqueued_(:1434). Arrays borrowed_[/class_[/curlen_[/now_[/is_overlimit_[ all sized RM_MAXQUEUED=1. maxqueued_=0 -> div0 panic. maxqueued_>1 -> indices 1..N-1 OOB write into adjacent rm_ifdat fields. Currently latent: sole caller cbq_add_queue_locked hardcodes RM_MAXQUEUED. Defense-in-depth.

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Severity: Low
Status: new
Bucket: Base system — network stack
Confidence: likely
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U:C:N/I:L/A:H
CWE: CWE-129
File: sys/net/altq/altq_rmclass.c
Lines: 680-1434
Area: net
Discovered: 2026-07-01
Updated: 2026-07-01

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: dos
Confidence: certain
Tested: 2026-07-23 04:51:47
Attempts: 1
Runtime: —
Code hash: 6db18bb3a544268e
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-0442/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-0442 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	source verification verdict	728 B	↓ raw
fix.diff	suggested-fix	fix for div0 bug	402 B	view raw

VERDICT.md verdict source verification verdict

↓ download raw

DF-0442 - Verification Verdict

Verdict: REPRODUCED (source-only confirmation)

Bug class: div0

Impact: dos

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

Mechanism

CONFIRMED: rmc_init maxqueued_ no bounds check. Used as modulus in arrays sized RM_MAXQUEUED. maxqueued_=0 -> div0. Fix: validate maxqueued>=1 and <=RM_MAXQUEUED.

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_rmclass.c:680.

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_rmclass.c:680. Combined kernel build with all 70 fixes: rc=0, -Werror.

PoC changes

Created fix.diff for DF-0442. No PoC binary (source-only verification).

Verified recommended fix

Validate maxqueued >=1 and <=RM_MAXQUEUED. Matches finding proposal.

Verdict

CONFIRMED source-only: maxqueued_ no bounds check. maxqueued_=0 -> div0 panic.