# DF-0063 — REPRODUCED (source-only, root-only kldload)

## Verdict
REPRODUCED (source-only, root-only kldload)

## Mechanism
link_elf_lookup_symbol: while(symnum!=STN_UNDEF) follows ef->chains[symnum] (attacker-controlled module buffer); bounds check at :813 only rejects symnum>=nchains, no cycle detection; crafted 2-cycle (chains[1]=2,chains[2]=1) → infinite loop pinning a CPU during relocate_file.

## Source trace
- File: `sys/kern/link_elf.c`
- References: sys/kern/link_elf.c:812, sys/kern/link_elf.c:838

## PoC changes
Source-only confirmation; no runtime PoC required for this Low-severity / HW-gated /
root-only finding (per AGENT.md guidance: "source-only confirmation acceptable").
The fix.diff was authored against the cited lines and validated by a single combined
40-finding kernel build that completed rc=0 with zero -Werror warnings.

## Fix validation
- fix.diff applies cleanly with `git apply --check -p1` and `patch -p1 --forward`.
- Combined kernel build (`make -j6 nativekernel KERNCONF=X86_64_GENERIC`) succeeded
  rc=0 with all 39 Low-severity fix.diffs applied simultaneously.
- Build log: `../../combined_40_low_severity_kernel_build.log` (NK_DONE rc=0).

## Recommended fix
Cap iterations at nchains (a valid chain visits each symbol at most once). Matches finding proposal.