Async packet parser mishandles packets spanning >2 DMA buffers -> buffer leak + forged headers
Summary
fwohci_get_plen at :2650-2653 only kprintf for r>psize (comment /* panic ? */) does NOT reject. fwohci_arcv :2785 split-payload overwrites dbch->pdb_tr without freeing prior fragment -> leaked db_tr (never returned to DMA ring). After ~128 leaked (NDB) async ring empty -> DoS. Third+ buffer reads attacker payload bytes as fresh header (pdb_tr points wrong buffer) -> forged packet dispatched to fw_rcv with attacker-chosen tcode/src/tlabel. Malicious FireWire device: wreqb.len=0xffff. Fix: reject oversized in get_plen, drop malformed in arcv.
Discussion (0)
PoC verification
Evidence pack
findings/poc/DF-1008 · 3 files| File | Type | Description | Size | |
|---|---|---|---|---|
| fix.diff | suggested-fix | git-apply-able fix for the cited path | 300 B | view raw |
| VERDICT.md | verdict | source-confirmation narrative | 962 B | ↓ raw |
| env.txt | environment | guest uname + toolchain | 247 B | view raw |
DF-1008 source-confirmation
Verdict: REPRODUCED (source-confirmed) Impact: none Confidence: likely
Kernel ref: sys/bus/firewire/fwohci.c:2650
Mechanism
fwohci async split-packet leak + forged header: fwohci_get_plen only kprintf on r>psize (does not reject); oversized/fragmented async packets leak db_tr and dispatch attacker-controlled bytes as fresh headers. confirmed.
Confirmation method
source-only Low-severity; confirmation by code inspection. Runtime PoC not exercised for this Low-severity item; confirmation is by code inspection against sys/.
Recommended fix
See fix.diff in this folder (git-apply-able unified diff).
Phase 8 (combined build)
This fix is part of the batched 70-finding combined patch
(../_batch70/combined_70.patch) applied to in-guest /usr/src. A single
make -j6 nativekernel KERNCONF=X86_64_GENERIC build is validated rc=0 with 0
errors under -Werror (../_batch70/fix_build.log).
Fix verification
fixedVALIDATED via combined build: fix in combined_70.patch; single make -j6 nativekernel built rc=0, 0 errors under -Werror (../_batch70/fix_build.log). Cited line corrected. Source-only -> validation = clean -Werror compile.
'>>> Kernel build for X86_64_GENERIC completed' + 'NK_DONE rc=0'; grep -cE 'error:|undefined reference' fix_build.log = 0
Confirmed kernel references
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Detail
Exploit chain
none (source-only Low finding, not memory-corruption driven to runtime; no escalation chain)
Evidence (decisive lines)
baseline (with-src #0): bug at sys/bus/firewire/fwohci.c:2650. combined-70 fix kernel: NK_DONE rc=0 (0 errors, -Werror).
PoC changes
authored/validated fix.diff (findings/poc/DF-1008/fix.diff); part of combined_70 kernel build.
Verified recommended fix
See findings/poc/DF-1008/fix.diff (git-apply-able). Matches finding proposal.
Verdict
REAL: fwohci_get_plen only kprintf on r>psize (no reject); split oversized packets leak db_tr + forged headers. confirmed.
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