# DF-3231 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 triggerable without a device I/O failure in the root-volume-header reload window: the mount holds no permanent rootvol reference, so between transactions the refcount cycles to zero, hammer_rel_volume clears ondisk, and the next transaction starter reloads the header with bread - which fails only on failing/removable media. All three starters handle that failure solely with KKASSERT(error == 0) (no-op on production builds), after which trans->rootvol NULL flows into ~25 deref sinks (vol0_next_tid, undomap, volume stats, fsid, hammer_rel_volume). Fault injection is unavailable on this guest. Fix converts the three assertions into explicit panics with a message on all builds; compile-validated.

## Kernel references
- sys/vfs/hammer/hammer_transaction.c:53
- sys/vfs/hammer/hammer_transaction.c:79
- sys/vfs/hammer/hammer_transaction.c:109

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

## Fix

explicit panic on root-volume reload failure on all builds

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 (needs induced device I/O error in the header-reload window)

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.