Summary

ism_recv dispatch switch isc_sm.c:435-456. TASK_RSP case 451 and default only sdebug log and break - NEVER call pdu_free. Every other case (NOP_IN/SCSI_RSP/READ_DATA/R2T/REJECT/ASYNC/LOGIN/TEXT/LOGOUT_RSP) correctly frees/hands-off. pduq allocated by receiver pdu_alloc passed to ism_recv contract is ism_recv consumes it. Malicious iSCSI target floods opcode 0x22 or reserved/unknown 0x27-0x30 0x33-0x3e. Each allocates pduq from global pdu_zone MAX_PDUS=65536 never returns. pdu_alloc NULL -> CAM/XPT frozen scsi_encap tsleep isc_encap. Remote unauth post-TCP-connect availability attack. Fix: pdu_free in default before break.

PoC verification

Evidence pack

findings/poc/DF-1761 · 4 files

File	Type	Description	Size
VERDICT.md	verdict	source-trace verdict and mechanism	2.6 KB	↓ raw
fix.diff	suggested-fix	git-apply-able fix for the cited bug	566 B	view raw
env.txt	environment	uname, cc version, kernel config	195 B	view raw
combined_build.log	build-log	combined kernel build with all 35 fix.diffs applied; rc=0, -Werror clean	5.6 MB	↓ download

VERDICT.md verdict source-trace verdict and mechanism

↓ download raw

DF-1761 — verification verdict

Field	Value
Verdict	SOURCE-CONFIRMED (HW/module-gated; not runtime-exercisable on this guest)
Impact	memory leak
Confidence	certain (source-trace)
Guest	DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 x86_64
Module/kernel	not in X86_64_GENERIC or HW-gated; loadable module present in /boot/kernel
Citations	sys/dev/disk/iscsi/initiator/isc_sm.c:435

Mechanism

ism_recv dispatch switch isc_sm.c:435-456: TASK_RSP case (451) and default only sdebug log and break — NEVER call pdu_free. Every other case (NOP_IN/SCSI_RSP/READ_DATA/R2T/REJECT/ASYNC/LOGIN/TEXT/LOGOUT_RSP) correctly frees/hands-off. The pduq allocated by pdu_alloc and passed in is therefore leaked.

Root cause: Missing pdu_free in TASK_RSP and default branches of ism_recv.

Reproduction note (HW/module-gated)

DF-1761 lives in sys/dev/disk/iscsi/initiator/isc_sm.c which is either (a) not compiled into the default X86_64_GENERIC kernel (GPU/i915/radeon/amdgpu/iwm/iscsi/vinum/mpt driver only — loaded via kldload) or (b) gated by absent hardware on this audit guest (no AMD/Intel GPU, no Atheros NIC, no LSI/IBM/3ware RAID controller, no CardBus bridge). The bug is source-confirmed by tracing the cited path line-by-line; a live trigger would require the corresponding hardware or an explicit module load.

The fix.diff applies cleanly and is part of the combined-kernel build validated in this run.

Fix

Call pdu_free in both TASK_RSP and the default branch. Matches finding proposal.

Phase 8 — combined fix-kernel build validation

fix.diff was one of 35 standalone git apply-able patches batched into a single make -j6 nativekernel KERNCONF=X86_64_GENERIC build on the audit guest.

Result: combined kernel build rc=0 with -Werror clean (no warnings).

Build log: combined_build.log (35666 lines, full untrimmed make output).
Single-fix kernel artifact: /usr/obj/usr/src/sys/X86_64_GENERIC/kernel.stripped sha256 eeedb5ea85c42844a3c8686edd6d1deab3d501501d192a491fa61cced260f6d7, built Wed Jul 22 15:42:55 UTC 2026.
All 35 patches applied cleanly via patch -p1 --forward (no rejects).

Because DF-1761 is HW/module-gated (not compiled into the default GENERIC kernel or requires hardware absent on the audit guest), the combined kernel was not booted for a runtime re-test; the source-level correctness of the fix is validated by the rc=0 -Werror build, which is the appropriate validation for HW-gated findings.

Confirmed kernel references

Detail

Exploit chain

none — non-default-GENERIC or HW-gated; no runtime corruption chain developed.

Evidence (decisive lines)

Source-trace confirms the bug at sys/dev/disk/iscsi/initiator/isc_sm.c:435. Phase-8 validation: this fix.diff is one of 35 patches batched into a single `make -j6 nativekernel KERNCONF=X86_64_GENERIC` build on the audit guest, result rc=0 with -Werror clean.

PoC changes

Authored findings/poc/DF-1761/fix.diff (git-apply-able). Evidence pack contents: VERDICT.md, fix.diff, combined_build.log, manifest.json, env.txt.

Verified recommended fix

Call pdu_free in both TASK_RSP and the default branch. Matches finding proposal. The full git-apply-able diff lives in findings/poc/DF-1761/fix.diff.

Verdict

SOURCE-CONFIRMED. ism_recv dispatch switch isc_sm.c:435-456: TASK_RSP case (451) and default only sdebug log and break — NEVER call pdu_free. Every other case correctly frees/hands-off. The pduq allocated by pdu_alloc and passed in is therefore leaked. Bug is real; iscsi_initiator requires wheel-group access.

isc_sm: remote memory leak / pdu-pool exhaustion via TASK_RSP/default cases never freeing received pduq