# DF-3234 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

Environment not provisionable on this guest: the trigger needs an EXT2_INCOMPAT_64BIT filesystem whose allocation returns blocks above 2^32 (>= 4 TiB at 1K blocks, >= 16 TiB at 4K blocks) - the four EFBIG returns in ext2_balloc fire only there, and each leaks the ext2_alloc result (bitmap bit set, group/free counters moved, i_blocks charged, nothing rolled back, no ext2_blkfree). The defect is line-certain by inspection (contrast the bwrite-failure path at :225 which does call ext2_blkfree), and the guest lacks both the disk space and an ext2 mkfs in base. Fix adds blkfree + unlock before each EFBIG return; compile-validated.

## Kernel references
- sys/vfs/ext2fs/ext2_balloc.c:135-136
- sys/vfs/ext2fs/ext2_balloc.c:169-170
- sys/vfs/ext2fs/ext2_balloc.c:215-218
- sys/vfs/ext2fs/ext2_balloc.c:258-261

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

## Fix

ext2_blkfree + EXT2_UNLOCK before each EFBIG return

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 (needs >= 4TiB 64BIT ext2 volume)

run: n/a

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.