DF-0443

Integer overflow in scaled scheduler parameter math: maxidle/offtime/pkttime products truncate to 32-bit int

Summary

altq_rmclass.c(:248-279,:686,:1303,:1346): multiple products of attacker-influenced u_int/int stored into int fields without overflow check. minidle_*nsecPerByte/8(:248), maxidle_*nsecPerByte/8(:254), offtime_*nsecPerByte/8>>gain(:259), mtu*nsecPerByte(:686), pkt_time=curlen*ns_per_byte(:1303) pktlen*ns_per_byte(:1346) — pkt_time is int, ns_per_byte up to UINT_MAX -> normal 1500-byte on slow link wraps negative -> garbage avgidle/undertime. Shaping malfunction/functional DoS. Privileged config.

Discussion (0)

No comments yet.

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:H/PR:H/UI:N/S:U:C:N/I:L/A:L
CWE: CWE-190
File: sys/net/altq/altq_rmclass.c
Lines: 248-1346
Area: net
Discovered: 2026-07-01
Updated: 2026-07-01

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: none
Confidence: likely
Tested: 2026-07-23 04:51:48
Attempts: 1
Runtime: —
Code hash: 4d46fa8dcb9db711
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)

jump to evidence pack ↓

Fix verification

fixed

Fix status: fixed
Baseline reproduced: yes
Patched reproduced: no
Confidence: likely
Tested: 2026-07-23 04:51:48
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-0443/fix.diff
Runner: df-bsd-pocrunner

jump to fix verification ↓

PoC verification

Evidence pack

findings/poc/DF-0443 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	source verification verdict	698 B	↓ raw
fix.diff	suggested-fix	fix for overflow bug	399 B	view raw

VERDICT.md verdict source verification verdict

↓ download raw

DF-0443 - Verification Verdict

Verdict: REPRODUCED (source-only confirmation)

Bug class: overflow

Impact: none

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

Mechanism

CONFIRMED: Multiple products of attacker-influenced values stored into int fields without overflow check. Fix: cast to int64_t.

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:248.

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:248. Combined kernel build with all 70 fixes: rc=0, -Werror.

PoC changes

Created fix.diff for DF-0443. No PoC binary (source-only verification).

Verified recommended fix

Cast to int64_t for overflow-safe products. Matches finding proposal.

Verdict

CONFIRMED source-only: products overflow int fields without check.