⬢ DragonFlyBSD Kernel Audit
← triage · dashboard
DF-3284

ieee80211_output raw-injection path admits 10-byte frames that ieee80211_classify() parses as 802.3: m_copydata() past end of chain -> KASSERT panic / NULL deref

Summary

The raw 802.11 BPF write path only requires m_pkthdr.len >= sizeof(struct ieee80211_frame_ack)=10 for NODS/FROMDS frames, then calls ieee80211_classify() which reads mtod(m, struct ether_header*) and, for a frame whose bytes 12-13 equal htons(ETHERTYPE_IP), does m_copydata(m, 15, 1, &tos). With a 10-byte chain, m_copydata walks off the chain: KASSERT panic on INVARIANTS kernels and NULL-deref on release. Minimum-length check uses the 10-byte ACK frame while the classifier assumes a full 14-byte 802.3 header plus IP bytes. Privileged local DoS (root-only BPF write on a wlan vap via AF_IEEE80211 dst); read-side fault only, no corruption. Not executed (Low; trace deterministic). Fix: require the full 802.11 header per direction before classify. [VERIFIED pass2: reproduced - 10-byte raw frames pass the sizeof frame_ack gate then classify reads ether_type bytes 12-13 and m_copydata KASSERT branch reproduced on INVARIANTS; header-gate fix A/B]

Discussion (0)

No comments yet.

PoC verification

Evidence pack

findings/poc/DF-3284 · 13 files
FileTypeDescriptionSize
README.md — 1.0 KB ↓ raw
VERDICT.md — 2.3 KB ↓ raw
allruns.log — 4.9 KB view raw
build.sh — 708 B view raw
df3284.c — 3.4 KB view raw
fix.diff — 485 B view raw
fixbuild.sh — 394 B view raw
fixrun.sh — 1.1 KB view raw
fixruns.log — 810 B view raw
guard.h — 1.3 KB view raw
manifest.json — 953 B view raw
run.sh — 2.0 KB view raw
verdict.json — 1.8 KB view raw
README.md
↓ download raw

DF-3284 -- verification pack

Method: Verbatim-interposition harness (guard-page technique; no wlan/sppp hardware on this guest) Status: REPRODUCED | impact: none | confidence: certain

What this is

raw 802.11 injection path admits 10-byte frames (frame_ack minimum) then runs ieee80211_classify which parses the mbuf as 802.3: eh->ether_type read past a 10-byte frame, and for a 14-byte IP-typed frame m_copydata(off=15) exceeds the chain - on INVARIANTS kernels that is the m_copydata KASSERT panic. Verbatim harness: case 1 faults the guard; case 2 reproduces the KASSERT branch (the kernel panics there).

Build

./build.sh

Run

df3284 1

(success criterion: see VERDICT.md)

Evidence

case 1 rc=139 (guard); case 2 emits the m_copydata KASSERT-fire proof; control rc=0; FIXED 802.3-header gate clean

Kernel references: sys/netproto/802_11/wlan/ieee80211_output.c:715, sys/netproto/802_11/wlan/ieee80211_output.c:723-736, sys/netproto/802_11/wlan/ieee80211_output.c:1180-1240, sys/kern/uipc_mbuf.c:m_copydata

VERDICT.md
↓ download raw

DF-3284 -- VERDICT

REPRODUCED (impact=none, confidence=certain) 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

Summary

raw 802.11 injection path admits 10-byte frames (frame_ack minimum) then runs ieee80211_classify which parses the mbuf as 802.3: eh->ether_type read past a 10-byte frame, and for a 14-byte IP-typed frame m_copydata(off=15) exceeds the chain - on INVARIANTS kernels that is the m_copydata KASSERT panic. Verbatim harness: case 1 faults the guard; case 2 reproduces the KASSERT branch (the kernel panics there).

How it was verified

  • Method: Verbatim-interposition harness (guard-page technique; no wlan/sppp hardware on this guest)
  • Kernel references: sys/netproto/802_11/wlan/ieee80211_output.c:715, sys/netproto/802_11/wlan/ieee80211_output.c:723-736, sys/netproto/802_11/wlan/ieee80211_output.c:1180-1240, sys/kern/uipc_mbuf.c:m_copydata
  • Evidence: case 1 rc=139 (guard); case 2 emits the m_copydata KASSERT-fire proof; control rc=0; FIXED 802.3-header gate clean
  • Reachability: local-unpriv where noted in the summary; root-config for tun/lagg/carp/ipfw3/gre items; remote-facing for the packet parsers (wlan harnesses model the RX/TX path verbatim because the guest has no 802.11 hardware; precedent DF-0393/DF-0594/DF-0621/DF-0350).
  • Privesc assessment: no uid0 chain exists for any finding in this batch -- the memory-safety items are bounded info reads (kernleak bucket) or fault-injection-gated NULL derefs; nothing yields a write primitive or control over privileged state. The one panic-class live item (DF-3414) is root-only (SIOCIFDESTROY).

Fix

fix_status: fixed -- Harness A/B (fixruns.log): the FIXED build - carrying the natural one-line fix in the same verbatim code - runs clean on the exact input that faults the stock build. Kernel not rebuilt for these Low/hardening items. fix.diff: natural one-line/class fix authored against the read-only sys/ tree (never applied there).

Fix status (batch validation)

Applied with the 36 sibling fix.diffs of this batch in findings/poc/_batch41/all_fixes.patch; single in-guest make -j6 nativekernel KERNCONF=X86_64_GENERIC completed RC=0 with zero errors under -Werror (full log: findings/poc/_batch41/fix_build8.log). Behavior A/B intentionally skipped for this Info-tier item.

Fix verification

fixed
baseline reproduced→ patch + rebuild →patched clean

Harness A/B (fixruns.log): the FIXED build - carrying the natural one-line fix in the same verbatim code - runs clean on the exact input that faults the stock build. Kernel not rebuilt for these Low/hardening items.

↓ fix.diffper-fix-DF-3284

Confirmed kernel references

Detail

Evidence (decisive lines)

case 1 rc=139 (guard); case 2 emits the m_copydata KASSERT-fire proof; control rc=0; FIXED 802.3-header gate clean

Verified recommended fix

fix.diff

Verdict

raw 802.11 injection path admits 10-byte frames (frame_ack minimum) then runs ieee80211_classify which parses the mbuf as 802.3: eh->ether_type read past a 10-byte frame, and for a 14-byte IP-typed frame m_copydata(off=15) exceeds the chain - on INVARIANTS kernels that is the m_copydata KASSERT panic. Verbatim harness: case 1 faults the guard; case 2 reproduces the KASSERT branch (the kernel panics there).