# DF-0099 — REPRODUCED (source-only, boot-time root only)

## Verdict
REPRODUCED (source-only, boot-time root only)

## Mechanism
vfs_mountroot_try: vfsname=kmalloc(MFSNAMELEN=16) devname=kmalloc(MNAMELEN=80); format ksprintf(patt,"%%%d[a-z0-9]:%%%ds",MFSNAMELEN,MNAMELEN) → "%16[a-z0-9]:%80s". subr_scanf CT_CCL writes width chars + NUL, so %16[...] writes 17 bytes into vfsname[16] (1-byte overflow); %80s similarly overflows devname.

## Source trace
- File: `sys/kern/vfs_conf.c`
- References: sys/kern/vfs_conf.c:430, sys/kern/vfs_conf.c:431

## 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
Use MFSNAMELEN-1 and MNAMELEN-1 in the format so width+1 == buffer size. Matches finding proposal.