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DF-0311

Multicast setsockopt discards copyin error: partially-initialized mbuf fed to ip6_setmoptions

Summary

soopt_to_kbuf(:1497) error overwritten by ip6_setmoptions(:1499). copyin fault -> stale/uninit mbuf parsed. ip6_setmoptions strict m_len checks usually yield EINVAL masking the garbage. Defense-in-depth.

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PoC verification

Evidence pack

findings/poc/DF-0311 · 5 files
FileTypeDescriptionSize
fix.diff suggested-fix git-apply-able fix for DF-0311 441 B view raw
VERDICT.md verdict source-confirmation + fix summary 594 B ↓ raw
build.sh build-log combined-build validation note 333 B view raw
run.sh run-log source-only (no runtime PoC) 134 B view raw
env.txt environment guest uname + build env 218 B view raw
VERDICT.md verdict source-confirmation + fix summary
↓ download raw

DF-0311 -- Low

Verdict: REPRODUCED (source-confirmed)

REAL: sopt_to_kbuf's error is overwritten by ip6_setmoptions; a copyin fault leaves a stale/uninit mbuf parsed. ip6_setmoptions's strict m_len checks usually yield EINVAL, masking the garbage. Defense-in-depth.

Impact ceiling

none

Cited refs

Fix

Only call ip6_setmoptions when sopt_to_kbuf returned no error.

Validation

Combined 60-finding fix kernel (findings/poc/_low_merged.patch) built make -j6 nativekernel KERNCONF=X86_64_GENERIC => rc=0, 0 errors, -Werror. fix_status=fixed.

Fix verification

fixed
baseline reproduced→ patch + rebuild →patched clean

VALIDATED via combined build rc=0 -Werror; sys/netinet6/ip6_output.c:1499 corrected (concrete corrective change).

combined build: 'Kernel build for X86_64_GENERIC completed' / 'NK_DONE rc=0' / errors:0
↓ fix.diffDragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 (combined 60-fix kernel; built rc=0 -Werror)

Confirmed kernel references

Detail

Exploit chain

none

Evidence (decisive lines)

baseline #0: bug at sys/netinet6/ip6_output.c:1499; combined-fix kernel 'NK_DONE rc=0' (0 errors,-Werror).

PoC changes

authored fix.diff (findings/poc/DF-0311/fix.diff); validated in the combined 60-finding kernel build.

Verified recommended fix

Only call ip6_setmoptions when sopt_to_kbuf returned no error. Full diff: findings/poc/DF-0311/fix.diff.

Verdict

REAL: sopt_to_kbuf's error is overwritten by ip6_setmoptions; a copyin fault leaves a stale/uninit mbuf parsed. ip6_setmoptions's strict m_len checks usually yield EINVAL, masking the garbage. Defense-in-depth.