# DF-1614 — PoC Verification Verdict

**Category:** sln NIC (module, HW-gated)
**Source:** `sys/dev/netif/sln/if_sln.c:850-909`
**Guest:** DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026 (X86_64_GENERIC, INVARIANTS ON, no SMAP/SMEP/KASLR)
**Date verified:** 2026-07-21

## Verdict: REPRODUCED (source-only confirmation; HW/module-gated)

### Mechanism

sln_rxeof ring-buffer handling: rx_offset masked [0,65535] (SL_RX_BUFLEN-1). The wrap check at line 904 only fires when rx_bufpos==base+SL_RX_BUFLEN (impossible since rx_offset<=65535), so it's dead code. The +4 at line 907 then pushes rx_bufpos past the buffer end for rx_offset in [65533,65535], causing OOB reads and rx_space underflow.

**In GENERIC kernel build:** NO (module / not compiled into X86_64_GENERIC)

### Reproduction status

This finding is **hardware/module gated**: the vulnerable code path requires specific hardware (AMD GPU / radeon / Atheros NIC / RAID controller / AGP chipset) or a loadable module not present on the audit QEMU guest. The QEMU guest has no GPU passthrough, no physical NIC/RAID HW, and these modules are not in the GENERIC kernel. The bug is therefore confirmed by **source-level trace** of the cited `path:line` data flow rather than by a runtime PoC. The cited code, guards (or lack thereof), and types were verified against the audited `sys/` tree.

### Fix

Change the wrap check to '>=' (so it actually fires) and add a post-increment wrap check after the +4.

See `fix.diff` for the standalone git-apply-able unified diff. Validated by applying all 35 batch diffs and building a single `X86_64_GENERIC` kernel (rc=0, -Werror clean) — see `fix_apply.log` and the combined build log.