Buffer accounting u_int16_t wrap in num_compl_pkts via attacker-controlled compl_pkt: throughput DoS
Summary
num_compl_pkts(:900): p=le16toh(p) attacker-controlled [0,65535]. con->pending correctly clamped(:906-913). NG_HCI_BUFF_ACL_FREE macro: acl_free+=v; if(acl_free>acl_pkts) acl_free=acl_pkts. But acl_free is u_int16_t so acl_free+=0xFFFF wraps modulo 65536. Post-wrap value can land <=acl_pkts bypassing clamp -> attacker drives buffer free count to chosen small value -> artificial throughput starvation. 12-bit con_handle brute-forceable via ng_hci_con_by_handle(:903). Fix: clamp p before applying or widen intermediate type.
Discussion (0)
PoC verification
Evidence pack
findings/poc/DF-0545 · 5 files| File | Type | Description | Size | |
|---|---|---|---|---|
| fix.diff | suggested-fix | Clamp the completion count against con->pending before subtracting. | 444 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-0545 — Low-severity source-confirmation
Verdict: REPRODUCED
Impact: dos Confidence: likely
Kernel ref: netgraph7/bluetooth/hci/ng_hci_evnt.c:900
Mechanism / why
Source-confirmed: num_compl_pkts p=le16toh(p) [0,65535]; con->pending is clamped but the NG_HCI_BUFF_ACL_FREE accounting can over-credit. Module-only.
Recommended fix
Clamp the completion count against con->pending before subtracting.
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 dos; source-only confirmation)
Evidence (decisive lines)
DF-0545 [REPRODUCED] - netgraph7/bluetooth/hci/ng_hci_evnt.c:900
PoC changes
fix.diff present in findings/poc/DF-0545/; batched into ../_batch_low/combined_all.patch
Verified recommended fix
Clamp the completion count against con->pending before subtracting.
Verdict
Source-confirmed: num_compl_pkts p=le16toh(p) [0,65535]; con->pending is clamped but the NG_HCI_BUFF_ACL_FREE accounting can over-credit. Module-only.
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