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DF-1920

Cleanup loop reads uninitialized stack arrays when copyin fails partway through SGL loop

Summary

L153-156 ioctl_data_tag/dmamap/mem/phys_addr[MAX_IOCTL_SGE=16] declared on stack without initialization. copyin fails at iteration k goto out L263. Cleanup L354 iterates full sge_count calling bus_dmamap_unload/bus_dmamem_free/bus_dma_tag_destroy with uninitialized stack slots for i>k where iov_len!=0. Conditional guards if(phys_addr[j])/if(mem[j]!=NULL)/if(tag[j]!=NULL) read garbage -> deref garbage pointers. Operator-group trigger: valid SGL[0] unmapped addr iov_len=8 all sgl[1..15] iov_len=8. Deterministic panic. Fix: ={0} initialize arrays.

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PoC verification

Evidence pack

findings/poc/DF-1920 · 2 files
FileTypeDescriptionSize
fix.diff suggested-fix git-apply-able unified diff; validated as part of combined 41-finding kernel build (rc=0, -Werror clean) 1023 B view raw
VERDICT.md verdict source-only confirmation + HW/module gating explanation 1.5 KB ↓ raw
VERDICT.md verdict source-only confirmation + HW/module gating explanation
↓ download raw

DF-1920 Verification

Verdict

SOURCE-CONFIRMED, INCONCLUSIVE-RUNTIME (HW/module gated).

The cited defect exists in the audited source at sys/dev/raid/mrsas/mrsas_ioctl.c:153-363. Reproduction on the running guest is not possible because the affected code path is gated behind hardware that is not present in the audit QEMU/KVM guest (no AMD/i915 GPU, no LSI MegaRAID, no MMC/SDHCI controller, no FireWire, no ATAPI floppy, etc.) and/or lives in a kernel module that is not loaded on the GENERIC-running guest.

Mechanism (source-only confirmation)

mrsas IS in GENERIC but no LSI MegaRAID HW in guest. Source: L153-156 declares ioctl_data_tag/dmamap/mem/phys_addr[MAX_IOCTL_SGE=16] on stack WITHOUT initialization. If copyin fails at iteration k, goto out at L263. Cleanup L354 iterates the full sge_count calling bus_dmamap_unload/bus_dmamem_free/bus_dma_tag_destroy with uninitialized entries from iterations >k.

Initialize all four arrays with = { 0 } / = { NULL } at declaration.

The full git apply-able diff lives in fix.diff in this folder; it was applied as part of a single combined 41-finding kernel build that compiled cleanly (rc=0, -Werror clean) — see ../fix_build_summary.txt.

Build validation

  • git apply --check on this fix.diff: OK
  • Combined kernel build (X86_64_GENERIC, INVARIANTS ON) with all 41 findings' fix.diffs applied: rc=0, no warnings, no errors.
  • The patched kernel was not booted/run because the affected code path requires hardware that the audit guest does not have.

Confirmed kernel references

Detail

Exploit chain

none — non-corruption classes (info leak / DoS / div0 / logic) or HW/module gated. No memory-corruption primitive reachable from userspace on this guest.

Evidence (decisive lines)

Source-only confirmation. Combined kernel build with all 41 fix.diffs applied: === NK_DONE rc=0 === at Wed Jul 22 18:05:21 UTC 2026 (no errors, no warnings). See findings/poc/fix_build_summary.txt.

PoC changes

Authored findings/poc/DF-1920/fix.diff (minimal targeted guard). VERDICT.md and manifest.json written. fix.diff validated by combined build.

Verified recommended fix

Initialize all four arrays with = { 0 } / = { NULL } at declaration. Full git-apply-able diff in findings/poc/DF-1920/fix.diff; validated as part of combined 41-finding kernel build (rc=0).

Verdict

SOURCE-CONFIRMED, INCONCLUSIVE-RUNTIME. The cited defect exists at sys/dev/raid/mrsas/mrsas_ioctl.c:153-363. mrsas IS in GENERIC but no LSI MegaRAID HW in guest. L153-156 declares ioctl_data_tag/dmamap/mem/phys_addr[MAX_IOCTL_SGE=16] on stack WITHOUT initialization. If copyin fails at iteration k, goto out L263. Cleanup L354 iterates full sge_count calling bus_dmamap_unload/bus_dmamem_free/bus_dma_tag_destroy with uninitialized entries from iterations >k. HW gated.