DF-0407

setsockopt(IP_OPTIONS) overwrites copyin error: parses stale mbuf data as IP options on copyin failure

Summary

ip_ctloutput IP_OPTIONS(:1097-1118): error=sopt_to_kbuf(...); error=ip_pcbopts(...). Second assignment overwrites first error. If sopt_to_kbuf fails (EFAULT unmapped ptr), MGET buffer NOT zeroed, ip_pcbopts parses stale heap data as IP options. If stale bytes satisfy loose syntax (mult4, valid LSRR/SSRR), stored in inp_options, emitted on subsequent packets. Probabilistic kernel heap info leak via IP options. Fix: check error before ip_pcbopts; use M_DONTWAIT|M_ZERO.

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Severity: Low
Status: new
Bucket: Kernel memory leaks / uninitialized disclosure
Confidence: likely
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N
CWE: CWE-457
File: sys/netinet/ip_output.c
Lines: 1097-1118
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 04:51:45
Attempts: 1
Runtime: —
Code hash: de2988945b358744
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 04:51:45
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-0407/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-0407 · 2 files

File	Type	Description	Size
VERDICT.md	verdict	source verification verdict	729 B	↓ raw
fix.diff	suggested-fix	fix for logic bug	406 B	view raw

VERDICT.md verdict source verification verdict

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DF-0407 - Verification Verdict

Verdict: REPRODUCED (source-only confirmation)

Bug class: logic

Impact: none

Source file: sys/netinet/ip_output.c

Mechanism

CONFIRMED: ip_ctloutput IP_OPTIONS overwrites sopt_to_kbuf error with ip_pcbopts. Failed copyin leaves MGET buffer uninitialized. Fix: check error before ip_pcbopts.

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/netinet/ip_output.c:1111.

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/netinet/ip_output.c:1111. Combined kernel build with all 70 fixes: rc=0, -Werror.

PoC changes

Created fix.diff for DF-0407. No PoC binary (source-only verification).

Verified recommended fix

Check error before calling ip_pcbopts. Matches finding proposal.

Verdict

CONFIRMED source-only: sopt_to_kbuf error overwritten by ip_pcbopts. Stale heap data parsed.