# DF-3267 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

DIOCCHANGEADDR with PF_CHANGE_REMOVE of the only pool address of an active nat rule panics immediately: pool->cur = TAILQ_FIRST(&pool->list) is NULL after the removal and the very next PF_ACPY(&pool->counter, &pool->cur->addr.v.a.addr, ...) dereferences it - live: Fatal user address access from kernel mode from rmpool, Fatal trap 12 page fault, fault virtual address 0x0, in the ioctl path. The same NULL rpool->cur would later be dereferenced unguarded on the packet path by pf_map_addr (pf.c:2693-2712) and pf_set_rt_ifp (pf.c:3642/3649) once the ioctl line is guarded, so the fix covers both sides (refuse to empty a live pool + NULL guard in pf_map_addr). Root-triggered panic today, defense-in-depth for the remote path.

## Kernel references
- sys/net/pf/pf_ioctl.c:2330-2333
- sys/net/pf/pf.c:2693-2712
- sys/net/pf/pf.c:3642-3649

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

## Fix

refuse removal of the last pool address + NULL guard in pf_map_addr; the ioctl-side guard makes the same call return EINVAL

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

## Reproduction

build: guest: cc -O -o rmpool rmpool.c (uses <net/pf/pfvar.h>)

run: guest: kldload pf; pfctl -f nat.conf (nat on lo0 ... -> 1.2.3.4); ./rmpool

expected: Fatal trap 12 page fault, fault address 0x0, in the DIOCCHANGEADDR ioctl (see panic.txt)

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

include path is <net/pf/pfvar.h> on this tree and needs <net/if.h> first for IFNAMSIZ; PF_CHANGE_REMOVE = 5, PF_NAT = 4 per the pfvar enums

## 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.