# DF-3105 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

Empirically refuted as unreachable on the current tree, with a crafted >4GB image proving both gates. A UDF image with a 5.37GB file (5x0x3FFFF000 extents + 8KB, markers 0xBB/0x55/0xCC placed) mounts fine and stat reports the full 64-bit size (5368696832), but: (1) read() at offsets >= 2^31 never reaches udf_bmap_internal - the int fsize truncation (udf_read :396, DF-0833 territory) clamps the loop first (pread at 0x100000000 returns 0/EOF silently); (2) mmap of ANY UDF file returns EINVAL because the filesystem never calls vinitvmio - vp->v_object stays NULL and vm_mmap.c:271 rejects (verified with mmap at offset 0). With the only two callers (udf_read path gated below 2^31 by the int fsize, mmap disabled entirely) unable to present an offset >= 2^32, the uint32 parameter truncation at udf_bmap_internal:1066 is dead on DragonFly today. The width bug is real latent code (FreeBSD takes off_t).

## Kernel references
- sys/vfs/udf/udf_vnops.c:399
- sys/vfs/udf/udf_vnops.c:845
- sys/vfs/udf/udf_vnops.c:1066
- sys/vm/vm_mmap.c:271

## Fix
See fix.diff.

## 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.