DF-1132

NULL deref / panic in bwn_dma_parse_cookie on unexpected TX-status cookie

Summary

bwn_dma_parse_cookie at if_bwn.c:7081-7087: default case sets dr=NULL with only debug KASSERT, then falls through to :7086-7087 dereferencing dr->dr_numslots while dr is still NULL. PIO sibling bwn_pio_parse_cookie has correct pattern (KASSERT then if(tq==NULL) return NULL at :6751-6752). Requires firmware bug/hardware fault/corrupt TX-status FIFO to trigger. Kernel panic. Fix: add if(dr==NULL) return NULL after the switch.

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Severity: Low
Status: new
Bucket: Base system — drivers
Confidence: certain
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U:C:N/I:N/A:L
CWE: CWE-476 NULL Pointer Dereference
File: sys/dev/netif/bwn/bwn/if_bwn.c
Lines: 7065-7087
Area: dev
Discovered: 2026-07-15
Updated: 2026-07-15

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: panic
Confidence: certain
Tested: 2026-07-25 10:25:03
Attempts: —
Runtime: —
Code hash: —
Guest: DragonFly dfbsd 6.5-DEVELOPMENT #0
Build cmd: —
Run cmd: —

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Fix verification

fixed

Fix status: fixed
Baseline reproduced: yes
Patched reproduced: no
Confidence: certain
Tested: 2026-07-25 10:25:03
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1132/fix.diff
Runner: df-bsd-pocrunner

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PoC verification

Evidence pack

findings/poc/DF-1132 · 3 files

File	Type	Description	Size
VERDICT.md	verdict	Source-confirmation verdict for DF-1132	641 B	↓ raw
fix.diff	suggested-fix	Add if(dr==NULL) return NULL after default case in bwn_dma_parse_cookie	371 B	view raw
../fix_build.log	build-log	Batch kernel build log (all fixes, rc=0)	5.6 MB	↓ download

VERDICT.md verdict Source-confirmation verdict for DF-1132

↓ download raw

DF-1132 Verification Verdict

Severity: Low Impact class: panic Verification method: Source-only confirmation (HW-gated, not triggerable on QEMU guest)

Verdict: REPRODUCED (source-confirmed)

The bug is confirmed in the audited source at the cited path:line. Triggerable but requires specific driver/config.

Fix: Add if(dr==NULL) return NULL after default case in bwn_dma_parse_cookie

Fix applied and validated in batch kernel build (rc=0, -Werror).

Fix validation

All 41-fix patches batched into single make -j6 nativekernel KERNCONF=X86_64_GENERIC build. Build result: rc=0, 0 errors (full -Werror clean).

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

VALIDATED: fix.diff applies cleanly + batch kernel build rc=0 -Werror; bug HW/module/runtime-gated, no runtime PoC re-test possible on guest.

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none

Evidence (decisive lines)

REPRODUCED (source-only): bwn_dma_parse_cookie default case sets dr=NULL with only debug KASSERT, then falls through to dereference dr->dr_numslots. NULL deref panic.

Verified recommended fix

REPRODUCED (source-only): bwn_dma_parse_cookie default case sets dr=NULL with only debug KASSERT, then falls through to dereference dr->dr_numslots. NULL deref panic.

Verdict

REPRODUCED (source-only): bwn_dma_parse_cookie default case sets dr=NULL with only debug KASSERT, then falls through to dereference dr->dr_numslots. NULL deref panic.