⬢ DragonFlyBSD Kernel Audit
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DF-3343

Unclamped ic_txstream*8-1 indexes const ieee80211_htrates[77] in ieee80211_media_setup — OOB read up to ~1.9KB past the array on driver/HAL misconfiguration

Summary

ieee80211_media_setup computes i = ic->ic_txstream * 8 - 1 and reads ieee80211_htrates[i].* without clamping i to IEEE80211_HTRATE_MAXSIZE-1. ieee80211_htrates is a const array of exactly 77 entries. ic_txstream is a driver-set uint8_t; the only guard is an INVARIANTS-only KASSERT in a different call path (set_mcsset, reached only via ht_attach), and chan_init merely defaults 0->2. Production kernels do no validation: a driver value >10 (e.g. 255) yields i up to 2039 - an OOB read of adjacent kernel .rodata/.data. Concrete in-tree route: if_ath.c:1148-1150 assigns ic_txstream from ath_hal_getcapability(HAL_CAP_STREAMS) whose failure return is explicitly discarded - a HAL quirk/failure leaves it garbage. The read value only feeds maxrate -> ifp->if_baudrate (weak read-only oracle); no write primitive, no user-controlled index, boot/module-load time only. Requires misconfigured/buggy driver (or out-of-tree); not user-triggerable. Fix: clamp the index + check the ath HAL return. [VERIFIED pass2: reproduced via guard harness - txstream 20 reads entry 159 of the 77-entry htrates table; driver-gated 1-4 in stock; clamp fix A/B]

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PoC verification

Evidence pack

findings/poc/DF-3343 · 13 files
FileTypeDescriptionSize
README.md — 784 B ↓ raw
VERDICT.md — 2.1 KB ↓ raw
allruns.log — 4.9 KB view raw
build.sh — 708 B view raw
df3343.c — 2.2 KB view raw
fix.diff — 312 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 — 818 B view raw
run.sh — 2.0 KB view raw
verdict.json — 1.5 KB view raw
README.md
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DF-3343 -- 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

ieee80211_media_setup indexes ieee80211_htrates[77] with ic_txstream*8-1 and no clamp; a driver/HAL value of 20 reads entry 159 (82 entries past the const table). Driver-gated (stock drivers program 1..4); verbatim harness with the real table shape faults the guard page.

Build

./build.sh

Run

df3343 oob

(success criterion: see VERDICT.md)

Evidence

control (txstream=4 -> index 31) rc=0; txstream=20 -> index 159 rc=139; FIXED clamp clean

Kernel references: sys/netproto/802_11/wlan/ieee80211.c:1620-1629, sys/netproto/802_11/_ieee80211.h:388

VERDICT.md
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DF-3343 -- 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

ieee80211_media_setup indexes ieee80211_htrates[77] with ic_txstream*8-1 and no clamp; a driver/HAL value of 20 reads entry 159 (82 entries past the const table). Driver-gated (stock drivers program 1..4); verbatim harness with the real table shape faults the guard page.

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.c:1620-1629, sys/netproto/802_11/_ieee80211.h:388
  • Evidence: control (txstream=4 -> index 31) rc=0; txstream=20 -> index 159 rc=139; FIXED clamp 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-3343

Confirmed kernel references

Detail

Evidence (decisive lines)

control (txstream=4 -> index 31) rc=0; txstream=20 -> index 159 rc=139; FIXED clamp clean

Verified recommended fix

fix.diff

Verdict

ieee80211_media_setup indexes ieee80211_htrates[77] with ic_txstream*8-1 and no clamp; a driver/HAL value of 20 reads entry 159 (82 entries past the const table). Driver-gated (stock drivers program 1..4); verbatim harness with the real table shape faults the guard page.