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DF-0260

tcpopts_match/ipopts_match read options beyond m_pullup-guaranteed contiguous region

Summary

ipfw_setup_local(:3323) only m_pullup hlen+sizeof(tcphdr). tcpopts_match(:1296-1301) walks th_off options from offset hlen+20 without additional pullup. Reads up to 40 bytes past contiguous region. Non-TCP/UDP/ICMP: no pullup at all(:3342-3344). Remote: attacker sends packet with large th_off. Reads stale mbuf data -> misclassification. OOB under non-standard mbuf layouts.

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PoC verification

Evidence pack

findings/poc/DF-0260 · 5 files
FileTypeDescriptionSize
fix.diff suggested-fix git-apply-able fix for DF-0260 456 B view raw
VERDICT.md verdict source-confirmation + fix summary 656 B ↓ raw
build.sh build-log combined-build validation note 333 B view raw
run.sh run-log source-only (no runtime PoC) 160 B view raw
env.txt environment guest uname + build env 218 B view raw
VERDICT.md verdict source-confirmation + fix summary
↓ download raw

DF-0260 -- Low

Verdict: REPRODUCED (source-confirmed)

REAL: ipfw_setup_local only m_pullup's hlen+sizeof(tcphdr) for TCP, but tcpopts_match walks th_off options past that; non-TCP/UDP/ICMP get no pullup at all -> reads up to 40 bytes past the contiguous region. Remote defense-in-depth read.

Impact ceiling

none

Cited refs

Fix

PULLUP_TO(hlen + (th_off<<2)) when th_off indicates TCP options present.

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/net/ipfw/ip_fw2.c:3323 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/net/ipfw/ip_fw2.c:3323; combined-fix kernel 'NK_DONE rc=0' (0 errors,-Werror).

PoC changes

authored fix.diff (findings/poc/DF-0260/fix.diff); validated in the combined 60-finding kernel build.

Verified recommended fix

PULLUP_TO(hlen + (th_off<<2)) when th_off indicates TCP options present. Full diff: findings/poc/DF-0260/fix.diff.

Verdict

REAL: ipfw_setup_local only m_pullup's hlen+sizeof(tcphdr) for TCP, but tcpopts_match walks th_off options past that; non-TCP/UDP/ICMP get no pullup at all -> reads up to 40 bytes past the contiguous region. Remote defense-in-depth read.