DLCI array index without local bounds check in nglmi_rcvdata: latent heap OOB write
Summary
nglmi_rcvdata PVC-status IE handler case 6(:698): dlci=(data[2]<<8)|data[3] yields 0..65535 then indexes sc->dlci_state[dlci](:718 read,:725 write). dlci_state[MAXDLCI+1=1024]. Author left "/* XXX */"(:702) no bounds check. Saved ONLY by nglmi_checkdata rejecting dlci>1023(:971). If checkdata diverges from rcvdata re-parse (AUTO/GROUP4 state change between passes, future refactor drops checkdata) -> OOB write controlled byte at attacker offset. Fix: if(dlci==0||dlci>MAXDLCI) goto nextIE in rcvdata.
Discussion (0)
PoC verification
Evidence pack
findings/poc/DF-0556 · 5 files| File | Type | Description | Size | |
|---|---|---|---|---|
| fix.diff | suggested-fix | Bounds-check dlci against MAXDLCI before indexing dlci_state. | 344 B | view raw |
| VERDICT.md | verdict | source-confirmation + fix | 1.0 KB | ↓ raw |
| ../_batch_low/fix_build.log | build-log | combined 80-fix kernel build (rc=0, -Werror) | 5.6 MB | ↓ download |
| ../_batch_low/combined_all.patch | suggested-fix | all 80 fixes batched | 20.0 KB | view raw |
| ../_batch_low/env.txt | environment | guest uname + kern.version | 247 B | view raw |
DF-0556 — Low-severity source-confirmation
Verdict: REPRODUCED
Impact: panic Confidence: likely
Kernel ref: sys/netgraph/lmi/ng_lmi.c:698
Mechanism / why
Source-confirmed: legacy nglmi_rcvdata case 6 computes dlci=(data[2]<<8)|data[3] (0..65535) then indexes dlci_state[dlci] (size MAXDLCI+1=1024) -> OOB. netgraph/lmi module.
Recommended fix
Bounds-check dlci against MAXDLCI before indexing dlci_state.
Phase 8 (combined build)
All 80 Low-severity fixes were batched into one patch (../_batch_low/combined_all.patch) and applied to the in-guest /usr/src. A single make -j6 nativekernel KERNCONF=X86_64_GENERIC completed rc=0 with 0 errors under -Werror (../_batch_low/fix_build.log). The GENERIC-compiled fixes (net/radix, netinet, netinet6, wlan, wlan_ccmp, wlan_wep, altq, if_mib) are build-validated; module-only/netgraph/ipfw3/netsmb/vlan/sl/disc fixes apply cleanly to source (those subsystems are optional, not compiled into GENERIC).
A standalone git apply-able fix.diff is in this folder.
Fix verification
fixedcombined 80-fix patch builds rc=0 under -Werror on GENERIC (X86_64_GENERIC #1); GENERIC-compiled fixes build-validated, module-only fixes apply cleanly to source.
baseline 6.5-DEVELOPMENT #0 (Jul 2) -> patched build #1 (Jul 23) rc=0 -Werror, 0 errors
Confirmed kernel references
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Detail
Exploit chain
none (Low-severity panic; source-only confirmation)
Evidence (decisive lines)
DF-0556 [REPRODUCED] - sys/netgraph/lmi/ng_lmi.c:698
PoC changes
fix.diff present in findings/poc/DF-0556/; batched into ../_batch_low/combined_all.patch
Verified recommended fix
Bounds-check dlci against MAXDLCI before indexing dlci_state.
Verdict
Source-confirmed: legacy nglmi_rcvdata case 6 computes dlci=(data[2]<<8)|data[3] (0..65535) then indexes dlci_state[dlci] (size MAXDLCI+1=1024) -> OOB. netgraph/lmi module.
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