# DF-3126 verification

Kernel: DragonFly dfbsd 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC x86_64

## Bottom line

Not dynamically exercised: cd9660_vptofh/vget reachability requires an NFS export of a cd9660 mount (VFS_VGET is called only from the NFS file-handle path) and the memory-safety ceiling is traced to EIO: for an ino above 2^42 the int lbn truncation makes the lbn >= volume_space_size guard pass on negative values, but the subsequent bread at the negative lblktooff offset is contained by the device strategy bounds check. The observable defect is NFS file-handle aliasing (truncated ifid_ino binds handles to the wrong vnode). Fix widens the guard to off_t and the compile-validated patch is included.

## Kernel references
- sys/vfs/isofs/cd9660/cd9660_vfsops.c:774-775
- sys/vfs/isofs/cd9660/cd9660_vfsops.c:924

## Exploit chain
(none: availability/correctness finding; no privilege chain)

## Fix

off_t lbn guard + reject oversized ino

See fix.diff in this directory (git-apply-able against the read-only sys/
tree; applied only inside the disposable verification guest).

## Reproduction

build: n/a

run: n/a (requires NFS-exported cd9660 mount)

expected: n/a

## Notes on the PoC (what changed vs the finding sketch)

(none)

## Fix status (batch validation)
Applied with the 36 sibling fix.diffs of this batch in findings/poc/_batch41/all_fixes.patch; single in-guest `make -j6 nativekernel KERNCONF=X86_64_GENERIC` completed RC=0 with zero errors under -Werror (full log: findings/poc/_batch41/fix_build8.log). Behavior A/B intentionally skipped for this Info-tier item.