DF-0649

Per-node ~1.5 MB kernel-memory amplification via fixed NG_NETFLOW_MAXIFACES array

Summary

LATENT: module cannot link (DF-0647). NG_NETFLOW_MAXIFACES=USHRT_MAX=65535 (ng_netflow.h:37). struct netflow embeds ifaces[65535] directly (:253) each ~28 bytes. Constructor kmalloc(sizeof(*priv),M_WAITOK|M_NULLOK|M_ZERO) :172 = single ~1.8MB allocation + full zeroing pass. No upper bound on netflow nodes -> privileged user (ngctl mkpeer) grows kernel heap without limit -> VM exhaustion/OOM/livelock. Would become live if netflow.c ported. Fix: lower NG_NETFLOW_MAXIFACES to realistic 64/256 or convert to dynamic sparse table.

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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:N/A:H
CWE: CWE-789 Uncontrolled Memory Allocation
File: sys/netgraph7/netflow/ng_netflow.c
Lines: 172-253
Area: net
Discovered: 2026-07-02
Updated: 2026-07-02

Team triage

untriaged

priority: — · owner: —

PoC verification

inconclusive

Status: inconclusive
Reproduced: no
Impact: dos
Confidence: likely
Tested: 2026-07-23 07:34:33
Attempts: 1
Runtime: —
Code hash: adfa6ca2192319b8
Guest: DragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026
Build cmd: n/a (source-only)
Run cmd: n/a (source-only)

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PoC verification

Evidence pack

findings/poc/DF-0649 · 4 files

File	Type	Description	Size
VERDICT.md	verdict	source-confirmation + fix	992 B	↓ raw
../_batch_low/fix_build.log	build-log	combined 80-fix kernel build (rc=0, -Werror)	5.6 MB	↓ download
../_batch_low/combined_all.patch	suggested-fix	all 80 fixes batched	20.0 KB	view raw
../_batch_low/env.txt	environment	guest uname + kern.version	247 B	view raw

VERDICT.md verdict source-confirmation + fix

↓ download raw

DF-0649 — Low-severity source-confirmation

Verdict: INCONCLUSIVE

Impact: dos Confidence: likely

Kernel ref: netgraph7/netflow/ng_netflow.c:253

Mechanism / why

LATENT: module cannot link; struct netflow embeds ifaces[NG_NETFLOW_MAXIFTES=65535] directly -> multi-MB allocation. Source-confirmed in a non-linking module.

Recommended fix

Dynamically allocate/size ifaces instead of embedding 65535 entries.

Phase 8 (combined build)

All 80 Low-severity fixes were batched into one patch (../_batch_low/combined_all.patch) and applied to the in-guest /usr/src. A single make -j6 nativekernel KERNCONF=X86_64_GENERIC completed rc=0 with 0 errors under -Werror (../_batch_low/fix_build.log). The GENERIC-compiled fixes (net/radix, netinet, netinet6, wlan, wlan_ccmp, wlan_wep, altq, if_mib) are build-validated; module-only/netgraph/ipfw3/netsmb/vlan/sl/disc fixes apply cleanly to source (those subsystems are optional, not compiled into GENERIC).

Confirmed kernel references

Detail

Exploit chain

none (latent; source-confirmed)

Evidence (decisive lines)

DF-0649 [INCONCLUSIVE] - netgraph7/netflow/ng_netflow.c:253

PoC changes

fix.diff documented (fix in verdict) in findings/poc/DF-0649/; batched into ../_batch_low/combined_all.patch

Verified recommended fix

Dynamically allocate/size ifaces instead of embedding 65535 entries.

Verdict

LATENT: module cannot link; struct netflow embeds ifaces[NG_NETFLOW_MAXIFTES=65535] directly -> multi-MB allocation. Source-confirmed in a non-linking module.