DF-0374

config_red divides by (max_th-min_th) and max_th without zero/negative check: kernel panic via setsockopt

Summary

config_red(:1346-1350): x->c_1=ioc_fs->max_p/(ioc_fs->max_th-ioc_fs->min_th). If max_th==min_th -> div by zero -> #DE -> kernel panic. If DN_IS_GENTLE_RED and max_th==0: x->c_3=(SCALE(1)-max_p)/max_th -> div by zero. set_fs_parms ignores return value (:1447 "XXX should check errors"). Requires raw IP socket (root).

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Severity: Low
Status: new
Bucket: Base system — network stack
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:N/I:N/A:H
CWE: CWE-369
File: sys/net/dummynet/ip_dummynet.c
Lines: 1346-1350
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: likely
Tested: 2026-07-23 04:51:43
Attempts: 1
Runtime: —
Code hash: c18e958c1af0b417
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: likely
Tested: 2026-07-23 04:51:43
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-0374/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-0374 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	source verification verdict	689 B	↓ raw
fix.diff	suggested-fix	fix for div0 bug	470 B	view raw

VERDICT.md verdict source verification verdict

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DF-0374 - Verification Verdict

Verdict: REPRODUCED (source-only confirmation)

Bug class: div0

Impact: dos

Source file: sys/net/dummynet/ip_dummynet.c

Mechanism

CONFIRMED: config_red divides by (max_th-min_th). If equal, div-by-zero panic. Fix: check max_th>min_th before division.

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/dummynet/ip_dummynet.c:1346.

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/dummynet/ip_dummynet.c:1346. Combined kernel build with all 70 fixes: rc=0, -Werror.

PoC changes

Created fix.diff for DF-0374. No PoC binary (source-only verification).

Verified recommended fix

Add max_th<=min_th check before division. Matches finding proposal.

Verdict

CONFIRMED source-only: config_red divides by (max_th-min_th). max_th==min_th -> div0 panic.